The Project Gutenberg eBook of The Radio Boys On the Mexican Border, by Gerald Breckenridge

The development of radio telephony is still in its infancy at this time of writing in 1922. And yet it has made strides that were undreamed of in 1918. Experiments made in that year in Germany, and by the Italian Government in the Adriatic, enabled the human voice to be projected by radio some hundreds of miles. Today the broadcasting stations, from which nightly concerts are sent far and wide across the land, have tremendous range.

Estimates compiled by the various American companies making and selling radiophone equipment showed that in March of 1922 there were more than 700,000 receiving sets installed throughout the country and that installations were increasing so rapidly it was impossible to compute the percentage with any degree of accuracy, as the gains even from week to week were great.

When you boys read this the problems of control of the air will have been simplified to some extent. Yet at the beginning of 1922 they were simply chaotic. Then the United States Government of necessity took a hand. The result will be, eventually, that certain wave lengths will be set aside for the exclusive use of amateurs, others for commercial purposes, still others for governmental use, and so on.

In this connection, you will note that in the story Jack Hampton's father builds sending stations on Long Island and in New Mexico. This is unusual and requires explanation.

The tremendous growth of amateur receiving stations is due in part to the fact that such stations require no governmental license. A sending station, on the other hand, does require a license, and such license is not granted except upon good reasons being shown. It would be natural for the government, however, to give Mr. Hampton license to use a special wave length—such as 1,800 metres—for transoceanic radio experiments. Extension of the license to the New Mexico plant would follow.

DIRECTIONS FOR INSTALLING AN AMATEUR RADIO RECEIVING TELEPHONE

In order that the boy interested in radio telephony may construct his own receiving set, the Author herein will describe the construction of a small, cheap set which almost any lad handy at mechanics can build. Such a set should be sufficiently powerful to permit of successfully picking up the concerts and other programme entertainments being broadcasted frequently by stations throughout the country.

Two drawings are given herewith which will enable boys to visualize the appearance of the set, and will be of aid in following instructions.

Referring to Figure 1 let us examine first the construction of the receiving inductance marked L. The latter is shown in detail in Figure 2, and consists of a heavy piece of cardboard. The back of an ordinary writing pad will do.

First, draw the circle out with a compass to the diameter shown and then divide off the outside into an unequal number of divisions as shown. Draw a light pencil line through each of these marks to the centre of the circle. Now with your scissors cut out the disc, after which you cut the slots as shown.

The slots should be about one-quarter of an inch in width and of the depth shown in the drawing. Two such discs should be made and, when all cut out, should be given several coats of shellac to add stiffness and to improve the insulating qualities.

Now at your hardware dealer's buy one-quarter pound of No. 24 double, cotton-covered wire and proceed to wind the coils in the manner shown. Keep the windings even and avoid all joints throughout the length of winding.

When you have finished, mount the coils as shown in the drawing. Make sure that the windings on both coils run in the same direction. If you fail to do this, the set will not work.

For the detector, it is better to purchase a good make of galena detector at any radio supply store. If you are handy with tools, however, you can buy the galena and make your own detector. It will work with more or less satisfaction.

Your next need will be the condenser. The condenser consists of a series of aluminum plates, some of which are movable and the rest stationary.

Buy a small variable condenser. Its function is to tune the secondary circuit, which is accomplished simply by turning the knob. Such a condenser could not be made without the use of a good set of tools, and the author strongly advises it be bought instead of made at home in order to avoid trouble. The aluminum plates are spaced very closely and great care should be taken to avoid bending them, as they must not touch each other.

The aerial for this set should be about 60 to 100 feet in length and as high and clear of surrounding objects as possible. A simple porcelain cleat at either end, as shown in the drawing, will serve to insulate it sufficiently.

Your ground connection can be made best by wiring to the cold water pipe, although wiring to a steam or gas pipe will do almost as well.

You are now prepared to mount the various instruments in their proper locations. For your table instruments, get a good pine board about seven-eighths of an inch thick. Buy four binding posts and use one for the aerial wire, one for the ground wire, and two for the phones or head set.

To operate the set, first bring the hinged coil of wire close up to the fixed coil and adjust the detector until you can hear in your receivers the loudest click caused by the turning on and off of the key to a nearby electric light. If no light is available, a buzzer and dry battery should be used. When the detector is properly adjusted you will be able to hear the buzz quite distinctly in the head phones if the buzzer is not too far away.

The actual adjustment of the detector is rather a delicate job, and once it is in the proper position it is a good plan to avoid jarring it, as it is liable to get out of adjustment very easily.

Once the sensitive spot on your detector is found, slowly turn the knob on your condenser and at some spot on it you should be able to pick up signals of some sort, either of radiophone or spark. If the set does not work, then go over all your wiring and be sure that the windings of the two coils are both running the same way.

The above set will work well for short distances, say up to twelve or fifteen miles. Beyond that, however, it will not receive music unless you have unusual facilities for putting up an aerial to a considerable height and well clear of surrounding objects.

Such a set should be constructed at a minimum of cost and may later, after you have become familiar with the operation of radio appliances, easily be converted into a set of much greater range by the use of a vacuum tube as detector and may even, by slight changes, be given the much desired regenerative effects.

CHAPTER I

A CRY IN THE AIR

"That's right, Frank. But the weather has been bad for sending so great a distance for days. When these spring storms come to an end the static will lift and well stand a better chance to hear from him."

"Righto, Bob. Then, too, the Hamptons may not have finished their station on time."

The other shook his head. "No, Jack wrote us they would have everything installed by the 15th and that we should be on the lookout for his voice. And when he says he'll do a thing, he generally does it. It must be the weather. Let's step out again and have a look."

Taking off their headpieces, the two boys opened the door of the private radiophone station where the above conversation took place and stepped out to a little platform. It was a mild day late in June, and the sandy Long Island plain, broken only by a few trees, with the ocean in the distance, lay smiling before them. A succession of electrical storms which for days had swept the countryside in rapid succession apparently had come to an end. The clouds were lifting, and there was more than a promise of early sunlight to brighten the Saturday holiday.

A few moments more they chatted hopefully about the prospects, then re-entered the station.

Frank Merrick and Bob Temple were chums, a little under 18 years of age each. It was their bitterest regret that they had been too young to take any part in the World War some years before. Frank was dark, curly-haired, of medium height and slim, but strong and wiry. Bob was fair and sleepy-eyed, a fraction under six feet tall and weighed 180 pounds. A third chum and the leader of the trio was Jack Hampton, 19 years of age. He had gone to New Mexico several months before with his father, a mining engineer.

All three boys were sons of wealthy parents, with country estates near the far end of Long Island. Frank's parents, in fact, were dead, and he lived with the Temples. Mr. Temple was his guardian and administrator of the large fortune left by his father, who had been Mr. Temple's partner in an exporting firm with headquarters in New York City. Jack Hampton also was motherless.

The boys were keenly interested in scientific inventions, and were given every facility by Mr. Temple and Mr. Hampton for indulging their hobbies. Such indulgence required considerable sums of money, but the men believed the boys were worth it. In fact, both gentlemen were scientifically inclined themselves, and were able to give the boys much valuable advice.

When Mr. Hampton decided to go to Texas and New Mexico as the representative of a group of "independent" oil operators engaged in a bitter war with the Oil Trust known as the "Octopus," Jack begged so hard to be permitted to go along that his father let him quit Harrington Hall Military Academy two months before the end of the term.

It was agreed that when school ended, June 28, Frank and Bob should join Jack in the Southwest for their summer vacation. The two boys owned an airplane in which they hoped to make the trip when the time came. Mr. Temple, however, was dubious about letting them attempt to make so long a flight alone.

"But, Dad," Bob would argue, whenever the matter was discussed, "we'll be all right. We've made lots of flights without any accidents. We're as capable as anybody. You know yourself what the instructors up at Mineola told you. You say we are too young to fly away alone. But look at the young fellows that got to be 'aces' in the War! Not much older than we are now."

It must be confessed that Mrs. Temple thought little of the matter one way or the other. She had so many social duties to take up her time that there was little left for the boys. Accordingly, the boys had only Mr. Temple to persuade and they felt pretty certain of doing that in time. So the last two months of school were spent in poring over maps and routes, and in studying up on landing fields and flying conditions generally throughout the territory they would have to cover.

Much of this study for the proposed flight was carried on at the radiophone station on the Hampton estate. Mr. Hampton was an enthusiast about the development of radio telephony and it was through him the boys first had become interested in the subject. A year earlier he had built a powerful station for the purpose of making experiments in talking across the ocean. On that account the United States Government had granted him a special permit to use an 1,800 metre wave length.

Before leaving for the Southwest, Jack told the boys his father intended to build in Texas or New Mexico another radiophone station of similar wave length. This would enable Mr. Hampton to communicate with his New York confreres through his Long Island station. The big thing to the boys, however, was that they would be able to talk to each other across 2,000 miles of territory. Delays in construction in the Southwest had occurred, however, and communication between the two stations had not yet been established when our story opens.

As the boys re-entered the station after their inspection of the weather, Bob threw himself sprawlingly into a deep wicker chair and, picking up a book, began idly to turn the pages. Frank went to the table where the control apparatus was located and put on a headpiece. For a few moments there was silence, which Frank presently shattered with a loud cry of: "Bob. Bob. Come here."

"Put on a headpiece, Bob," said Frank in a voice of great excitement. "I believe Jack is trying to get us."

Excited as his chum, Bob clamped a receiver on his head, while Frank manipulated the "amplifier" and "detector" knobs on the control apparatus.

A variety of sounds greeted the boys at first, whistles, calls, and chattering coming to their ears. Then as their tuner searched out the higher regions of the air, they shut out the sounds of the low-range air traffic. There was a thin, shrieking sound. Then, that also disappeared. And then quite suddenly the listening, expectant boys heard Jack's voice speaking to them just as plainly as if he stood in the room.

"Hurray, Jack, sure we can hear you," cried Frank, bending forward to speak into the transmitter on the stand before him.

Then as Jack's voice continued calling without paying him any attention, he straightened up and laughed.

"Gee. I forgot," he laughed. Laying down his headpiece, he ran across the room; opened a door into the power house adjoining where the mechanic was dozing over his pipe and called to him to throw on the generator.

Galloping back, as the man obeyed, Frank again snatched up his headpiece. Bob already was bending over a transmitter, calling to Jack in faraway New Mexico. Both boys listened with straining ears for the response. Presently Jack answered: "I can hear you, but only very faintly. Put that band piece on the talking machine. You know the one I like so much. I can't think of its name. I'll tune to it."

Frank hastily shuffled through a pile of talking machine records. Finding the one he sought, he put it on the machine which stood directly in front of a big condensing horn strapped to the back of a chair to give it the proper height. A moment or two later, Jack's voice in the receivers declared:

"Oh, we've been working some days out here," answered Jack. "But we couldn't get you."

Jack's voice became excited. "Going?" he answered. "Fellows, I never knew what excitement was until this last week."

"Oh, I couldn't tell you now," laughed Jack. "It would take all day and then some to tell you all that's happening around here. But, let me tell you, between Dad's business opponents and a gang of Mexican bandits that appeared on the scene lately, things are getting pretty lively. Say, when are you coming? Now's the time if ever——"

Suddenly, Jack's voice ceased abruptly, to be succeeded a moment later by his agonized cry for "Help." Then there was a crash that rang in the eardrums of the alarmed boys listening in. Then, silence.

CHAPTER II

THE ENEMY NEAR

Frank Merrick and Bob Hampton looked at each other in alarm. Their faces were pale.

That cry for "Help" which abruptly had cut off Jack's voice as he spoke to them from his radiophone station 2,000 miles away in New Mexico still rang in their ears. Their heads still hummed from the vibrating crash which had succeeded. What did it all mean?

Frank snatched the receiver from his head, while Bob removed his more slowly. Frank voiced the question in each mind as he said in a tone of apprehension:

"Well, do you know what I think?" asked Frank with energy. "I think those Mexican bandits he spoke about sneaked up on him."

"Well, if they did, they caught a Tartar," said Bob, with conviction, remembering Jack's athletic prowess. All three boys were athletic, good swimmers, boxers and wrestlers, as well as skillful fencers. Jack, however, was unquestionably the superior of the others, except that Bob was the best wrestler.

Frank shook his head dubiously. "I don't know," he said. "If there was a bunch of them and if they sneaked up from behind while he was talking."

"Just the same," said Bob, "old Jack would put up some battle. I'll bet you the furniture got mussed up all right, all right. That's the reason for that crash. Probably the microphone was torn from the cords. They may even have wrecked the station. Boy, oh boy, don't I wish I'd been there." And Bob doubled up his fists and pranced around, making deadly swings at imaginary foes.

"Calm down, Bob," said Frank, dropping into a chair and running a hand through his hair as he was in the habit of doing when perplexed. "We don't know that it happened the way we figure. We don't know what happened. Maybe Jack was badly hurt, maybe he was killed. Or he may be a prisoner of the bandits.

"Oh," he cried, leaping to his feet and beginning to walk up and down the room distractedly, "isn't there something we can do? This is maddening."

"Calm down yourself, Frank," said Bob, always the cooler of the two in a crisis. "If we can't do any better, at least we can wire to Jack's father and find out in a few hours what happened."

At this moment the door was pushed open. A tall man of distinguished appearance, still in the prime of life, and bearing a close resemblance to Bob, entered the room. He glanced inquiringly at the boys.

It was Mr. Temple, Bob's father and Frank's guardian, and there was relief in the boys' voices as they greeted him. He always was so capable in an emergency.

"Motored home at noon today," he said. "Guess I've got spring fever. Anyhow, I couldn't stand it in the city. Della told me you were over here and that you thought, perhaps, you would hear from the Hamptons today." Della was Bob's younger sister, and the Temples' only other child.

"We heard all right, Dad," said Bob gravely. Thereupon he proceeded to relate what had occurred.

Mr. Temple listened in silence. His face showed he was disturbed. At the conclusion of Bob's recital, he walked over to a headpiece and put it on.

"No use, Uncle George," said Frank, but Mr. Temple turned to him with a twinkle in his eye.

"Oh, I'm bunged up a little," came back Jack's voice, in a cheerful tone. "But there are no bones broken."

"Was it the bandits?" demanded Bob, who had clamped on a third headpiece, as he elbowed Frank aside to speak into the transmitter.

"Yes. Three of them," responded Jack. "A scouting party. They sneaked in behind me. Thought I was alone, I guess, but when I hollered for help Dad came in from the power house on the run and the pair of us put them down for the count. We've got them tied up here now. The microphone cord was snapped but I was able to make repairs. So I started calling for you right away."

"Jack, this is Mr. Temple," cut in the older man at this point. "If your father is there, please put him on the phone. I'd like to speak to him."

Frank and Bob politely removed their headpieces and walked to a bookcase, talking in low tones, as they leaned their elbows on the top of it. This room, by the way, deserves a brief description.

It was circular and without windows. The walls were hung with a material resembling burlap in appearance, but of special construction and sound-proof. The ceiling was nine feet high. From a point six feet up the walls material like that in the walls stretched to a point in the middle of the ceiling. The room had somewhat the appearance of the interior of a small circus tent. This construction was for the purpose of increasing the acoustic properties.

While Mr. Temple conversed with Mr. Hampton, in whose oil operations he naturally was interested, as he had invested a considerable sum in them, the boys talked in whispers. They were frankly envious of Jack's adventures and wishing that they, too, were on the ground. Suddenly, something said by his father caught Bob's attention, and he stopped talking to Frank and turned to listen.

"Well, I'll tell you, Hampton," Bob heard his father say, "I've got a sharp attack of spring fever. I think I need a vacation. And if these two youngsters of mine will let me go along, I'll come out with them."

Bob couldn't control his eagerness. Going up to his father's side, he pulled insistently at his sleeve.

"Wait a minute, Hampton," said Mr. Temple. "Bob has something on his mind." He removed the receiver and regarded his son with a twinkle. "Out with it," he said. "I suppose that quite shamelessly you've been listening to my conversation."

"No, Dad, Honest Injun," protested Bob. "Only I couldn't help overhearing that part about you going with us. Say, Dad, we'll go by airplane, won't we?"

Mr. Temple groaned in mock dismay. "Run along," he said. "You'll drive me crazy with that airplane business." Then, once more adjusting his headpiece, he resumed his interrupted conversation with Mr. Hampton.

Bob returned to Frank, wearing a wide grin. "I couldn't resist putting over that piece of propaganda," he said.

"Say," answered Bob scornfully, "now that Dad has decided to go along, it's a cinch. He's as crazy about flying as Mr. Hampton is about the radiophone."

"Ssst. Ssst," came a warning whisper, interrupting them. They swung about to face the door into the power house. It was part-way open and the round good-natured face of Tom Barnum, filled now with anxiety, was framed in the opening. Tom was the mechanic-watchman. He beckoned, and the boys tiptoed across the room and into the power house, closing the door behind them. Old Davey, caretaker at the Hampton home, stood there, wringing his hands.

"Seed him myself with my own two eyes," quavered Old Davey, a little old man who was a pensioner of Mr. Hampton's. "He's a big dark ugly-lookin' feller. I seed him a-sneakin' into the house through the cellar door I left open to git out some garden tools."

"I run," said Old Davey, simply. "Leastways I tried to, but my legs ain't what they used to be."

Re-entering the sending room, Bob once more gained the attention of his father, who still was in conversation with Mr. Hampton. He told him what Old Davey had reported. Mr. Temple readjusted the headpiece and swung about to the transmitter.

"Anything in your house a fellow could carry off in a pocket, Hampton?" he said. "Because the boys tell me there is a thief in it right now, and we're going up to try to catch him."

"I don't think so," said Mr. Hampton, and then added in a tone of alarm: "Great guns, Temple, yes. There is. There's a duplicate list among my papers that the Octopus would give anything to obtain possession of. It's a list of the lessees out here in the oil fields who have joined the independents."

Removing the headpiece, he hurried Bob back into the power house. There he ordered Tom to switch off the motor, lock up and follow them. Then accompanied by the boys and with Old Davey trotting alongside to keep up, he started in swift strides for the Hampton house, which could be seen above the intervening tree tops, about a quarter of a mile away.

"I thought you came out from town for a little peace and quiet, Dad," said Bob. "You're certainly getting it, aren't you? Hey. There he goes." And with a shout, Bob started running swiftly toward the figure of a man who had just emerged from the open cellar door at the rear of the Hampton house.

CHAPTER III

A DARING LEAP

At Bob's shout the intruder who had just emerged from the Hampton cellar looked back over his shoulder. Seeing he was discovered he broke into a desperate run. He was heading toward the front of the house where ran the long and winding drive which led to the main highroad.

The man shouted hoarsely, and from the front of the house came the sound of a powerful motor engine being set in motion.

"He's got a car waiting for him," cried Bob, who was in the lead. "Drat the luck, he'll escape us yet."

"Hey, Bob, we can cut 'em off at the Gut," called Frank, and he struck away at a tangent from their course as the man disappeared around the house and the motor car could be heard roaring off down the drive.

Old Davey had dropped far behind and Mr. Temple and Tom Barnum were laboring along some yards in the rear of the two boys and steadily losing ground.

"Careful, boys," called Mr. Temple gaspingly, as he grasped the meaning of the boys' maneuver. "Don't be rash. May be several of them."

"All right, Dad," sang out Bob over his shoulder. "We'll be careful. Follow along."

The boys were heading for a place in the woods where the drive ran between six-foot banks before turning a sharp corner. Cars perforce had to be slowed up going through this place which the boys called the Gut. Furthermore, the drive approached this place by a winding, circuitous route, while the boys were not far distant from it by the shortcut through the woods which they were following. Chances were even that they would be in time to intercept the fugitives. Yet what could they do even if they arrived in time? They gave no thought to that as they crashed through the underbrush.

Bob slightly in the lead reached the top of the bank overhanging the road ahead of his comrade and experienced a thrill of triumph as he heard the roar of the approaching car and realized he had arrived first. The car slowed down as it entered the Gut. Evidently the driver remembered the perilous place from when he had driven through on approaching the house.

The car passed below going at a snail's pace while Frank was still a short distance in the rear and Mr. Temple and Tom Barnum were not yet in sight. It was an open touring car with the top folded back. There were three men in it, one on the seat beside the driver and the third in the rear. He was the man who had entered the Hampton house. The driver appeared to be a New York taxi chauffeur, and probably had been employed for the trip. The others were swarthy men, foreign in appearance.

The man beside the driver, looking up, saw Bob, and shouted. At that moment the car passed directly beneath him, and Bob leaped. He landed on the running board beside the rear seat. Steadying himself as the car lurched from the impact of his weight, Bob reached in and grasped the man on the rear seat by the coat collar and half pulled him from the car, so that his body lay across the door.

Then the unexpected occurred. The driver opened his throttle and the car leaped ahead, and at the same time the man beside him stood up and struck at Bob.

Bob leaned back to avoid the blow, and the next moment found himself flat on his back in the road, with the car disappearing around the curve.

Frank, who by now had reached the top of the bank, dropped to the road beside him and bent over him with real anxiety in his voice as he said:

Again there was a crashing in the underbrush on the top of the bank, and Mr. Temple and Tom Barnum came into view, red and perspiring.

"Escaped you, hey?" said Mr. Temple, leaping to the road, as Bob scrambled to his feet. "But, say, I see you captured something all right." And he pointed to a coat clutched fast in Bob's hand.

Then for the first time Bob noticed that in falling from the car he had dragged his victim's coat with him. He held it up and looked at it curiously.

"He must have been wriggling out of his coat when he found you wouldn't let go," surmised Frank. "I could see him threshing around just as I came up to the top of the bank. Then you fell and held on tight and the coat was pulled from him."

"Yes, I guess that's the way it happened," assented Bob. "Well, I'd rather have had the fellow. This isn't any good to me." And he tossed the coat away contemptuously.

"Not so fast, Bob," said Frank, stooping to pick up the garment. "Let's see what's in the pockets. There may be a clue as to the man's identity."

"That's right, Frank," said Mr. Temple. "Search it well. And, Bob, did you notice the license number of the car? We can telephone and have it intercepted."

Frank interrupted the conversation with a shout of delight. "Look at this," he cried, holding up a long strip of paper. "Return trip ticket to Ransome, New Mexico. And a wallet with a big bunch of bills in it. And here, what's this?" he added, holding up a thick, legal-looking envelope. "Why, Mr. Hampton's name is written on it."

"Let me have that, Frank," said Mr. Temple, extending his hand. Frank passed him the envelope. Mr. Temple noted the seal had been broken, and opening it he pulled out a thick document down which he ran his glance hurriedly. Then his face became grave.

"Boys," he said, "Mr. Hampton has many things of value in his home, but this was the most valuable of all." Briefly he explained the paper contained a list of names of "independents" in the oil field, together with other information, which would give the Octopus a very great advantage in the business war between the Oil Trust and the "independents" if the document fell into its hands.

"This is pretty serious business, boys," Mr. Temple continued. "Bob, you were very rash, but you did a good stroke of business that time. Come," he added, "we'll go back to the house, and call up the police. Maybe that car can be stopped and its occupants arrested."

As they turned through the woods, another thought occurred to Mr. Temple, and he asked Frank what was the name of the man to whom the railroad ticket had been issued.

"Jose Morales," read Frank. "This is the portion for the return trip from New York. Evidently the man came from—why, Mr. Temple, he came here from Ransome, New Mexico. That's the nearest station on the railroad to the Hampton's camp."

Frank thwacked Bob gleefully on the back. "Say, Bob," he declared, "old Jack isn't having all the fun after all, is he?"

CHAPTER IV

SHOTS AT THE STATION

"Boys," said Mr. Temple, when the Temple home, a short distance from the Hampton place, was reached, "come into the library with me. I want to have a serious talk with you."

Obediently, Bob and Frank filed into the room and sat down in deep leather armchairs, while Mr. Temple sat back in a swinging chair by his broad, flat-topped desk. Selecting a cigar from the humidor at his elbow, he lighted it and puffed thoughtfully several moments before addressing the chums.

"First of all," he said at the conclusion of this period of silence, "I've decided that we will not notify the police of this affair."

"We want to keep this matter to ourselves until we can see more clearly what it means," explained Mr. Temple. "We recovered what was stolen, anyhow. But more than that, I begin to suspect there is something more behind all this than mere business rivalry between the independent oil operators and the Trust."

"Well, boys, I'll tell you," said Mr. Temple, speaking deliberately and thoughtfully. "In the first place I know the men at the head of the so-called Octopus. They are keen business men and quick to seize every legitimate advantage. But they are above such unscrupulous tactics as this.

"I know the signs point to them as the instigator of our troubles at Mr. Hampton's camp and then here today. But those signs point to something else, too. If you will recall, Jack said the fellows who raided the Hamptons today, or rather tried to do so but failed, were Mexicans. And this man who entered the Hampton house today was a Mexican, too. What was his name, Frank?"

"Yes, Jose Morales," said Mr. Temple. "Well, I believe that certain Mexicans are responsible for our troubles, and not our business rivals, at all."

"In order to make trouble between the United States and Mexico," said Mr. Temple, promptly.

"Oh," said Bob, "I begin to see what you're driving at. You mean, then, that by attacking the independents in the Southwest these Mexicans would get us so stirred up that Uncle Sam would take a hand to protect our properties, and might even send troops to the border?"

"But in that case, Uncle George," demanded Frank, "why wouldn't the Mexicans be making trouble for the Octopus, too?"

"Because, Frank," explained the older man, "the properties throughout the region where we are located are mainly held by independent operators. The Octopus is trying to gobble us up, but it hasn't succeeded, and won't if we can prevent. But, just the same, it isn't there for the Mexicans to attack. If they want to harass anybody in the hope of getting the United States Government to intervene, they must attack us and our friends and allies."

"Yes, I see that now," said Frank, nodding. "But what makes you think the Mexicans want to get into a war with Uncle Sam?"

"They don't particularly yearn to come to blows with us, Frank," said Mr. Temple. "And not all Mexicans are involved, if my suspicions are correct, but only a faction. You see, boys, General Obregon has been President of Mexico now for several years, but the country is far from pacified and far from submitting to his rule. The rebel forces in the northern part of Mexico are gaining in strength right along. One of these days they will be in open revolution.

"Now these Mexicans who want to depose Obregon would like to get him into trouble with the United States in the hope that what they desire would then come to pass."

"I begin to understand you," said Bob, with more animation than usual. "You mean the rebels would like to stir up trouble on the border and get Obregon into hot water with Uncle Sam in just the same way that Pancho Villa some years ago made trouble between our government and Carranza by his raid on Columbus, New Mexico?"

"Gee, Dad," cried Bob. "This time, if there's a war, I'm going to enlist, believe me."

"Hurray for the young aviators of the Rio Grande," cried Bob, swinging his arm like a cheer leader of the school team.

"You boys don't know what you're talking about," said Mr. Temple, but with an indulgent smile. "I should imagine you would have read enough of the horrors of war during the past few years to make you never want to see a battlefield or shoot a gun at a man."

"That's right, Uncle George," said the sensitive Frank, shuddering as he recalled some of the things he had read of Europe's devastation.

"No, boys," said Mr. Temple, "if I am right about this, we'll have something more important to do than to fight battles or track bandits across the Mexican desert by airplane."

"Young man, you're in a hurry, aren't you?" smiled Mr. Temple. "Well, boys, I believe that by day after tomorrow I can have my affairs in order so that I can leave them for awhile. Then we'll start. That is, of course, if you'll carry me as a passenger."

"Will we carry him?" said Bob, striding to his side. "Good old Dad." And he thumped his father on the shoulder, a resounding blow that made the older man grimace humorously and draw away from him.

They were interrupted by a knock on the door. Frank opened the door to find a maid standing in the passage. She was trembling with excitement.

"Oh, Mister Frank," she gasped. "I heard several shots. Seemed like they came from the radiophone station of Mr. Hampton's. I'm so worried about Tom."

"That's right, Tom's your sweetheart, isn't he?" said Frank. The maid blushed. Frank re-entered the room, and explained the maid's message practically all in one breath.

"We were talking so much that we didn't hear the reports, I suppose," said Mr. Temple, jumping up and snatching at his hat. The boys already were at the door but he called them back. "This time," he said grimly, "I'm not going to have you taking any chances on being killed. You will wait for me, and please remember it." Opening a drawer, he drew out a heavy automatic, broke it open to assure himself it was loaded, and then dropped it in his coat pocket. "All right now," he said. "Let's go."

CHAPTER V

PLANS FOR THE FLIGHT

The boys needed no second bidding. Out of the door, down the passageway, and out of the house, they dashed. Then they headed across an intervening stretch of lawn for the radiophone station, concealed from sight by a clump of trees. Mindful of Mr. Temple's admonition not to rush into danger without him, they checked their pace. But the older man was making good time himself.

Through the woods they dashed, emerging within sight of the door of the power house. There stood Tom Barnum unharmed, revolver in hand. At the noise of their approach, he swung about abruptly, bringing up his revolver in doing so. Mr. Temple and the boys shouted, and he dropped the threatening weapon again to his side.

"What happened, Tom?" queried Mr. Temple, as they surrounded the watchman-mechanic in charge of the Hampton radiophone station with whom they had pursued a thief fleeing from the Hampton home only a short time before.

"Well, sir, when we come back from chasin' them fellers in the motor car," Tom explained, "I stopped at your back door a minute to chin Mary an' tell her the news. She wanted to know what all the excitement was about.

"Then I come on down here, an' thinks I to myself: 'I'll just get out the old army revolver that I carried in France an' I'll be better fixed for trouble the next time.' So I took 'er out of my locker in the shop here an' swabbed her up an' just got everything slicked when I hear a fellow creeping up to the door an' then voices whisperin' together.

"Then the door starts to open slow an' easy like. I seen somebody what hadn't no business here was nosin' around an' I says to myself: 'Tom, it's a good thing you got the ol' army gun fixed up in time.'

"Then one of 'em stumbles an' falls agin the door an' open she comes with him a-sprawlin' on the floor. The other fellow is right behin' him but he sees me an' lets out a yell an' turns an' runs. Man, he was a regular jackrabbit, too. I'll say that for 'im.

"Well, I been crouchin' by the dynamo an' let out a screech like wild Injun an' fired off a shot through the doorway. Maybe two shots. Say, you'd oughta seen that bird fly then. As for the other fellow, the one that stumbled an' fell, he picks himself up an' tuk out like a whitehead.

"I fired agin, high, just to scare 'em. I scared 'em all right, I guess. Anyhow, they disappeared over south there toward that old wood road that nobody uses no more. An' then I hear a motor car roar an' off she goes."

"Were," said Tom. "Dark-lookin' fellers an' one didn't have no coat. That was the guy Bob peeled his coat off of. I'd know 'em agin easy."

For several minutes there was an animated discussion of the exciting events of the afternoon. What puzzled Bob and Frank was the reason for the return of the thieves to the scene from which they had been driven. Nobody could offer a good solution of the mystery until finally Bob said:

"Say, I'll bet they were going to hide here in the station and lay for me in the hope of getting back that coat and the papers the thief stole from Mr. Hampton's house."

"Yes," put in Frank, "and the wallet with the railroad ticket to Ransome, New Mexico, and all that money, too."

"I believe you are right, boys," said Mr. Temple. "These certainly are no ordinary thieves, but desperate men."

"Dad," said Bob, who had been knitting his brow in thought, "according to what you believe, this is all part of a plot of certain Mexicans to embroil their country and ours by making trouble for the independent operators in the Southwest represented by Mr. Hampton. In that case, why should they try so hard to steal that list of the names of the independents. That looks to me like a move on the part of your business rival, the Octopus."

"I know it does, Bob," said his father. "The thing isn't clear to me by a good deal. But I believe I am right. However, let's go into the station now and call up the Hamptons out in New Mexico. Both Mr. Hampton and Jack will be interested to hear about what has happened here this afternoon."

The boys agreed enthusiastically, and with a word to Tom Barnum to switch on the motor in order that they might have power to telephone, all three entered the station. But, despite repeated calls, they received no response.

"I suppose so," said his father. "But this business has me worried. Let's hope nothing has gone wrong out there."

Reluctantly, all three abandoned their efforts, removed their headpieces, and with a "good-bye" to Tom, who lived in a room at the rear of the station, started for the house. If New Mexico were to call, a light bulb would flash the signal in Tom's quarters, and he would telephone the house.

It was twilight when they reached home, and all three went to their rooms to dress for dinner.

"Tomorrow," said Mr. Temple in parting, "we'll all drive over to church, and then in the afternoon you boys can go to work preparing the airplane, and I'll lend a hand." Mr. Temple was chairman of the Board of Trustees of an old ivy-covered church in a sleepy village some miles away, and never let Sunday pass without attending divine worship.

At dinner the talk was all of the prospective airplane flight to New Mexico. The events of the day were told in detail to Mrs. Temple and Della, Bob's sister. Della, who was an athletic girl of 16, declared she wanted to go with them, but Bob answered rudely, as boys too often speak to their sisters:

Mrs. Temple made no objections to the proposed trip, but began immediately to lay plans for filling the house with guests during their absence. And in discussion of the details, Della was appeased.

"Say, Bob, why are you so rude to Della?" Frank queried later, in the library, as they awaited Mr. Temple's coming to discuss preparations for the flight.

"Huh, she's not your sister, Frank," said Bob. "Anyhow, I believe you're sweet on her."

"No, I'm not," said Frank hotly, "but she's a good kid and you ought to treat her better."

"Yes, you are, too," said Bob. "I know you. But there's no use getting hot about it. Here comes Dad now," he added, as a familiar footstep sounded in the hall. "Let's get at those maps and guides and we'll dope this out together."

For several hours the discussion continued. For months the boys had been making their plans, going over routes, selecting landing fields, etc. Now that Mr. Temple had decided to accompany them, they laid their plans before him. He nodded, well satisfied in the main, but making a few pointed suggestions of value.

"And with the radiophone that we carry on the airplane," said Frank, "we can be in touch with Tom at this end and Jack out in New Mexico all the way. That all-metal body of the plane makes a fine ground, better than hanging wires possibly could. And with that new detector Bob and I have worked out, I'll bet we can hear all the way."

"Sure," said Bob, getting up and stretching, "Well, come on, Frank. Let's turn in. It's near midnight. I for one need a good night's sleep. And I hope there'll be no trouble to disturb us tonight."

CHAPTER VI

A THIEF IN THE NIGHT

Bob stirred under vigorous shaking, opened his eyes sleepily, and saw Frank bending over him. His chum had thrown a bathrobe over his pajamas. The door between their connecting rooms stood open. The early morning sunlight of a bright June day streamed in the open windows.

"Whazzamatter?" grunted Bob, and closing his eyes he turned over and prepared to snatch an extra forty winks. But Frank shook him again.

"Come on," said he. "Stir your stumps. We can slip out before anybody else awakes, grab something to eat in the pantry, and go down to the shed and tinker on the plane. Come on, Bob, we can get in a couple of hours work before going to church."

Bob was wide awake by now, and pleased at the prospect held out by his chum. Tumbling out of bed, he headed for the shower in the bathroom which the boys used in common, but Frank restrained him.

"Make too much noise," said Frank. "Anyhow, we can take a plunge down at the beach before going to the shed. Come on, get into some old duds and let's hurry."

The boys were dressed in short order. In the pantry, to which they tiptoed, they found cold tongue and ham, bread and butter, with which they hurriedly made several sandwiches apiece. It was not much of a breakfast, but their appetites were those of youth and they enjoyed it. Letting themselves out of the back door of the sleeping house, they started on a trot for the little private beach, a good half mile away. The last few yards were made with the boys shedding garments as they ran. Then with a shout they plunged naked into the rollers coming in from the open Atlantic.

It was great sport. For twenty minutes they crashed through breakers, wrestled, ducked each other, shrieked aloud secure in the knowledge there was nobody within hearing distance, and in general had a glorious time of it. At the end of that period they rubbed down briskly with rough towels until their bodies were in a healthy glow, then dressed and set out for the airplane shed.

This was located some distance back from the beach where a long, level stretch of sandy soil, unbroken by tree or bush, made an ideal landing field. The "shed," as the boys termed it, was, in reality, a substantial structure of corrugated iron, well-anchored to resist the severe Atlantic coastal storms. It stood to one side of the route followed by the boys in going from the house to the beach, with the rear to them, and was midway between the two points and concealed from the house by a clump of trees.

When the matter of buying a plane was up for discussion more than a year before, after the boys and Jack Hampton, their absent chum, as well as Mr. Temple—himself an enthusiast about flying—all had become licensed pilots by taking a course at the Mineola flying fields, the question had been whether to buy a hydroplane.

That question finally had been solved by the purchase of a light, all-metal plane capable of carrying two passengers besides the pilot and able to alight on water and land. It was not a stock model but was built after a special design. All three boys had flown it, as well as Mr. Temple, and none had ever had an accident. Equipped with a radiophone head set, to which had been added recently a detector designed by Bob and Frank to increase the receiving radius, this plane was the boys' especial pride.

What was their dismay, therefore, when they rounded the shed from the rear and found the great doors which they had left padlocked several days before standing open and the interior empty. For several moments they stood as if rooted to the ground, staring in stupefaction. Then Bob groaned, and Frank echoed him.

Frank was the first to recover from his dismay and ran forward to look at the broken padlock, dangling from one leaf of the great folding doors. "Cut through with a file," he called excitedly to his chum. "And this set of big bar locks above and below the padlock were cut the same way."

"I always said we should have had one of those rolling iron screens, fitting solidly into the ends of the side walls and rolling up into the roof," groaned Bob, passing on into the interior. "But what's the use locking the barn after the horse is stolen." Disconsolately he moved around the interior of the shed, as if expecting to find concealed somewhere the airplane which he could not yet bring himself to believe had been stolen.

"Great Scott, an Iron Cross," cried Frank, seizing the object held out. A German Iron Cross it was. "And here you can see how this ribbon frayed through and parted from the clasp," added Frank.

"Turn it over," said Bob. "If it's a real one given by the Kaiser it will have the recipient's name on it."

"Maybe it is," said Bob darkly. "But if that bird doesn't fly back with our airplane I'll make war on Germany myself."

Despite his gloom, Frank grinned. He slapped big Bob on the back. "Come on, old boy," he said. "No use hanging around here. We may as well go back to the house and report the latest mystery."

"I wonder," said Bob, as they set out, "whether there is any connection between the two—between this theft of our airplane and that stuff yesterday."

It was Mr. Temple who was able to provide an answer to that question. The boys found him up and dressed when they reached home, and himself considerably excited over a telephone call from New York City. He, too, was dismayed when told of the theft of the airplane. But when the boys showed him the German Iron Cross he hit the desk before him a resounding blow with his fist. Their conversation took place in the library.

"That fits right into the puzzle," said he. "Boys, while you were out of the house I had a long distance telephone call from New York City. The man who called said he was a chauffeur who had driven two men down here yesterday, that he thought they were on legitimate business, but that when Bob tried to stop them he saw they were bad ones, as he put it. Later, when they made him drive them over to the radiophone station and he heard Tom rout them with his pistol shots, he said he drove off as they ran for his car and left them. He inquired in the village and learned my name, and so called me up to clear himself in case I intended starting a pursuit.

"And he said," added Mr. Temple, leaning forward and speaking impressively, "that he was pretty certain one man was a Greaser and the other a Hun. Those were his own words. Of course, he meant one was a Mexican and the other a German."

"So when this chauffeur abandoned them they stole our airplane to get away," cried Frank excitedly.

"Maybe," said Bob, "I copped every cent they had in pulling that Mexican's coat off his back, and they were without carfare back to the city."

"Oh, I suppose the German had money," said his father. "The German probably was an aviator. And they stole the airplane in order to escape from here quickly before we could get in pursuit of them. I imagine they'll land in some deserted spot—plenty of them in the sandy reaches along the New Jersey coast, for instance—make their way to a railroad, after abandoning the plane, and go——"

"Weren't there a bunch of German spies in Mexico, stirring things up there against us, during the war? Well, I'll bet there are some of the same breed there now making all this trouble for Mr. Hampton," said Frank.

"A good idea," said Mr. Temple, approvingly. "Well, boys, there will be no church for us today. This matter has got to be attended to."

CHAPTER VII

KIDNAPPED

"Nor I, Frank. A fellow wouldn't believe that right here near New York, in the most densely populated part of the East, two men could steal an airplane and escape without a trace."

"Oh, I don't know, Bob. You remember last winter when that aviator from the upper end of Long Island was last seen flying across the Sound toward the Connecticut shore and was never seen or heard of again."

"But, Frank, here forty-eight hours have passed. Here we are, Tuesday morning. Dad has wired every city, town and hamlet in the East. Not a sign of the machine, nor of the men."

It was, in truth, Tuesday morning. The morning when, everything going as planned, they should have been setting out on their flight to the Hampton camp in New Mexico. Instead, the boys were moodily pecking at breakfast, the airplane had disappeared, and the trip seemed more and more remote.

To add to their worries, they had been unable to reopen communication with their chum, Jack Hampton, by radiophone, since that first and only time the previous Saturday afternoon. All their efforts to call him met with no response. The day before, moreover, a telegram had been sent Mr. Hampton by Bob Temple's father, informing him in code of recent mysterious occurrences, including the theft of the airplane, telling him the boys had tried to call Jack by radiophone, but without response from his powerful New Mexico station, and asking whether all was well with him. No answer had yet been received.

"Mister Robert," said Mary, the maid, entering the breakfast room, as the two boys sat in moody silence, "your father wants you and Mister Frank in the library."

The boys hurried to the library at once, where they found Mr. Temple, very grave of face, bent above a lengthy telegram which he had just finished decoding.

"It's from Jack," he said, "And the poor fellow is in a lot of trouble. Listen."

"Dear Friends, Father has been kidnapped. Two men in airplane carried him away into Old Mexico. Since getting your telegram few minutes ago realize it may have been your airplane. Wasn't there and didn't see it but description of machine given by cowboy on the range who saw it all tallies with description of your machine."

Mr. Temple paused for breath, and Frank, who had been computing mentally, interrupted.

"Our plane could do it all right," he said. "That is, if—When did this happen?"

"Well, they stole it sometime Saturday night," said Frank. "Yes, they wouldn't have had to make more than eighty miles an hour steady flying to do it. But where did they get the petrol?"

"Why," Bob reminded him, "we had her stocked with oil and gas. And the spare tanks filled, too. That wasn't impossible."

"Haven't answered your radiophone calls because didn't get them. Have been so busy running around in circles, haven't had time to watch the telephone. But if you call me when you get this shall be on the watch. Father was kidnapped Monday noon. No word from him. Need your help."

"He certainly does," said Mr. Temple, emphatically, as he concluded reading. "And he'll get it, too. Come on, boys, let's call him up."

Evidently Jack was on the watch for their signal, for he answered at once, and as soon as each had tuned to their private 1,800-metre wave length, the Temples and Frank were given the full details as to the kidnapping of Mr. Hampton.

He had been riding horseback across the range, miles from any oil derricks or pumping stations, on his way to visit one of the "independent" oil operators.

A lonesome cowboy hunting a stray was the only other human being in sight, and he was a half mile away. Suddenly out of the sky swooped an all-metal airplane, glistening in the sun. It made a beautiful landing on the sandy soil, bumped along over a few clumps of mesquite, and came to rest close beside Mr. Hampton. The latter jumped from his horse, and started running toward it. Evidently, Jack thought, his father believed the Temples and Frank had unexpectedly arrived.

Then the watching cowboy saw two men leap from the airplane and start for Mr. Hampton, who turned as if to run. Thereupon, one of the two pointed a revolver at him and he turned, perforce, and surrendered. He was put into the airplane, the two men again climbed aboard, and the machine soared up into the sky before the astonished cowboy could more than set his horse in motion.

"Only the cowboy who saw it and I," said Jack. "This cowboy knew father by sight, and came direct to me with the information. I've made him promise not to tell anybody until he hears from me."

"That's right, Jack," said Mr. Temple, very earnestly. "This information must not get out. I believe, Jack, your father will be safe from harm and that the men who seized him are intent on embroiling Mexico and the United States. Now we don't want any more wars, Jack, and we must try to get your father back without the aid of troops."

"Yes, sir," said Jack. "Father and I have suspected what the game was, and that was why I told the cowboy to say nothing."

"Good," said Mr. Temple, approvingly. "Now, Jack, that the mystery of the airplane's disappearance has been cleared up, we are ready to leave at once. We can get out of New York City on the 6 o'clock train tonight. Look for us Friday. I'll say good-bye until then, and let the boys speak to you, for I know they are dying to do so."

While the boys and Jack conversed, Mr. Temple sought out his wife. After explaining the necessity for his abrupt departure with the boys for New Mexico, he said:

"I should worry if I thought you would be subjected to annoyances while we were away. But I believe there will be no more trouble here. And with the servants in the house and the guests you have invited, you may feel perfectly safe."

"Oh, Dad, I think you're awfully mean not to take me along," pouted Della, who was present.

"Why, Lassie," said her father, "with a bunch of harum scarum boys to look after, my hands will be full enough."

"Yes, you think they're just boys," flashed his young daughter. "But you wait and see. They'll be taking care of you. Just you wait and see. Frank is awfully clever."

"I wish, George, that you wouldn't tease her about Frank," said Mrs. Temple. "She's such a child."

"Yes," said Mr. Temple, thoughtfully. "I suppose so. But," he added, "I'm glad she likes Frank."

CHAPTER VIII

HELD FOR RANSOM

The Temples, father and son, and Frank Merrick stood on the gravel-bed outside the little wooden box doing duty as station at Ransome, New Mexico. The transcontinental flier which had dropped them, was dwindling in the distance. Jack Hampton, whom the chums and Mr. Temple had crossed the country from New York to join, was in the center of the group. Greetings had been exchanged, they had all slapped each other on the back indiscriminately and enthusiastically, and now Bob Temple stood off at arm's length to admire his chum.

"Righto," agreed Frank, also gazing at the handsome Jack admiringly. "Where do you get 'em? Lead me to the store right away."

Jack, who was 19 and the oldest of the three chums, was almost as tall as the six-foot Bob, but of more slender build than that gridiron warrior. He had the build of a thoroughbred, long legs, flat hips, trim waist, deep chest and broad shoulders and a flat back. Both at dashes and distance running Jack easily was supreme at Harrington Hall Military Academy, which all three boys attended. Like Bob he was fair and had curling chestnut hair. His eyes were blue and lively, his features not too regular. Altogether, he was a striking figure.

Today he was dressed in khaki shirt and breeches. Instead of puttees he wore high, laced leather boots that reached to his knees. On his head, pushed back so that his wavy hair showed in front, was a wide-brimmed sombrero. By his side, suspended from a cartridge belt, swung an automatic revolver in its holster. This was the outfit so admired by his chums from the East, trim in their light-weight summer suits of the latest cut and wearing low tan shoes more adapted for city streets than for the sands stretching inimitably on every hand.

"We've worried considerably while aboard the train, Jack," said Mr. Temple, "for fear something dire might happen to you these last two or three days. I'm glad to see you are all right. Any word from your father?"

Jack shook his head in negation. "Not a word," said he, "since those two rascals picked him up in your airplane and headed for Old Mexico."

"Well, don't worry, Jack," said Mr. Temple. "I don't believe his life is in danger."

"I'm trying not to worry, sir," said Jack. "But now that you and the fellows are here, we shall have to get busy at once. It has been pretty hard to wait for you. I wanted to ride into Old Mexico myself at once."

Bags in hand the group was moving to the rear of the station, and now came in sight of a ramshackle automobile with a Mexican at the wheel, easily distinguished by his swarthy coloring and his ragged mustaches, as well as by his peculiar dress—a steep crowned hat like a sugar loaf, with a very wide brim, a tight bolero jacket that did not reach to the waist and disclosed a dark blue silken shirt beneath and tight-fitting trousers that flared at the bottom.

"That is Remedios and his flivver," explained Jack. "He does odd jobs all through this region. I hired him to take us out to camp. But before we climb aboard, take a look at this view."

Obediently, they paused and gazed at the surrounding country. In the foreground was a wide dirt street at the rear of the station. For the equivalent of the length of a city block it was lined on both sides with wooden structures one-story in height, but with the false fronts of the frontier country pretending to second stories—a front wall sticking above the roof and with the semblance of windows painted on it. A dry goods store, a Chinese laundry, an alleged hotel, several restaurants, several ex-saloons still carrying on some kind of business—these comprised the lot. At one end the street ran abruptly into the desert. At the other was a cluster of old freight cars made into dwellings, with Mexican men, women and children loitering in front in the sun. This was Ransome.

"Not much of a town," said Jack, "just a trading post for a wide stretch of this country around here. But look at the setting, will you?" And he swept a hand in a wide gesture indicating the horizon.

On every hand stretched the desert, broken by clumps of mesquite and cactus with the only trees in the landscape the thick belt of cottonwoods lining the banks of a stream that rose in the mountains to the north and ran by the town. North, east, south and west lofty mountains gleamed on the far horizon, while closer at hand rose the foothills. These latter were of fantastic shapes, like castles, tables or crouching animals, and of the most vivid coloring. Over all was the warm and brilliant sunshine of late afternoon. As for the air, it was clean and despite the warmth of the day already beginning to turn cool as the sun hovered on the rim of the farthest mountains to the west.

"Wait until you have known it day in and day out for months," said Jack. "You will never want to go back to Long Island."

"Oh, well, I suppose I'll want to go home sometime," said Jack. "But just the same, I'm in love with this country. As for the old-timers off there in the hills, you couldn't drive them away."

"Say, Jack," said Frank, as they all continued standing and gazing at the surrounding scene, "I thought we'd see some oil derricks around here. But there isn't one in sight."

"No, Frank," interposed Mr. Temple, in explanation, "you see the Independents are mainly located over in the Panhandle, or upper western portion of Texas and in Oklahoma. That is east from here. But Mr. Hampton had his geologists in through this region, and they reported the prospects for finding oil favorable. Then the Independents came in quietly and took up leases, and Mr. Hampton followed to prepare for development of the field."

"Say, Jack," said Frank, "I'm hungry as a hunter. If we are going to get dinner at your camp, let's move along. How far is it, by the way?"

"Ten miles," said Jack, leading the way toward the automobile with its dozing Mexican at the wheel. "Come on."

The others followed and were about to climb into the automobile when the rapid hoofbeats of a galloping horse ringing on the sun-baked clay of the street drew their attention, and they paused.

"Why, it's Gabby Pete," said Jack in surprise, moving forward a step as the rider reined up his horse so sharply that it reared and slid on braced hind legs. The animal came to rest so close to him that Jack was forced to give back a step, and it stood there snorting and blowing.

An oldish man of tremendous girth, but who sat his horse easily despite his size, grinned down at Jack. He was white-haired and under the brim of his sombrero little eyes twinkled genially and shrewdly in a round, fat face.

"What brings you here, Pete?" asked Jack, sharply. "I thought you were at camp, getting dinner for my guests." He indicated the boys and Mr. Temple, who stood close at hand, looking on. "Who will prepare dinner for them now?"

Gabby Pete, the talkative camp cook, scratched his head under his sombrero, and looked solemn. "Waal, they'll have ter wait a bit," he said. "But I kin rustle grub in a hurry onct I git back ter camp. An', anyhow, Mr. Jack, a feller came to camp a while ago in one o' them there aeryoplanes. Jest flew up almost to the door an' steps out an' gin me this yere letter." Here Gabby Pete produced a missive from the front of his shirt, and passed it to Jack. "He sez as how it war most partickler that you git it right away. So I rid in with it," said Gabby Pete, adding aggrievedly: "an' now you hop on me fur it."

Jack seized the missive in a sudden fever of anxiety. An airplane? He opened the letter, took in its contents at a glance, and turned excitedly to his chums.

CHAPTER IX

ON THE DESERT TRAIL

Eagerly Mr. Temple, Bob and Frank gathered around Jack, crowding to read over his shoulders the missive left at camp by a messenger in an airplane and brought to Ransome by Gabby Pete, the camp cook, following Jack, who had gone to the little New Mexican town to meet the party from the East.

The writing was cramped and foreign, as if the pen were wielded by a hand more accustomed to form German script than English letters. The missive was brief:

"Sir, this is to inform you that Mr. John Hampton is held in a secure place. One hundred thousand dollars must be paid for his release. A man riding alone must bring the money in United States bills of one thousand dollars each to the Calomares ranch two weeks from today. He must wear a white handkerchief in his hat."

"Pete, you heard me say something just now about my father being held for ransom. I believe you are my friend." Gabby Pete nodded violently. "Well, forget what you heard. If anybody asks you, remember that father has gone East on business."

"Sure, boy," said Pete. "I'm a tombstone. Well, me an' Angel Face here," and he slapped his horse affectionately, whereat Angel Face reared and pranced, giving the lie to her name, "we may as well git started fur camp so's to feed you when you arriv."

Jack laid a restraining hand on Pete's knee. "Wait just a minute, Pete. Do you know where the Calomares ranch is located?"

Pete nodded. "Aw, sure," he said, "that must be Don Fernandez y Calomares, down in Ol' Mexico. That's a good hundred mile acrost the border. It's in a valley in them mountains," he added, pointing to the darkening southern horizon.

"Waal," drawled Gabby Pete, plaintively, "I stick to hum so much o' the time I never git to talk to nobody nor hear the noos. But seems to me I did hear onct about him. Yes, sir, somebody sez as how Don Fernandez lives in a palace in that wilderness jest like a king of old, with armed ree-strainers or whatever you calls 'em——"

"Yes, that's the word. An' this feller what tol' me sez as how he's very proud and haughty-like an' has a beyootiful daughter, an'——an'——"

Pete dropped his voice, and paused, eyeing Remedios, the Mexican in the nearby flivver.

"Guess not," said Jack. "Why?" He, too, looked toward Remedios. The latter had his back to them and was blowing indolent wreaths of smoke from a brown paper cigarette.

"I don't trust that feller, that's all," whispered Gabby Pete hoarsely. "He's down acrost the border too much o' the time. Anyhow, as I was sayin', this yere Don Fernandez is agin the Obregon gov'ment an' backin' a new revolution. That's what the feller tol' me, anyhow. Waal, Mr. Jack, Angel Face an' me will go an' git dinner." And with a slap on his horse's flank that caused her to spin about and dash away, Gabby Pete was off.

"First thing is to get to camp, I guess," he said. "Then after dinner we can talk over what has to be done. What do you say?"

"He's got the biggest appetite for his size I ever saw," said Bob, affectionately, slapping his smaller chum on the back.

"I second Jack's motion," said Mr. Temple, seizing his bags and leading the way to the car. The others also picked up their bags and followed. "We know now that your father is safe, Jack," said Mr. Temple. "So the news in that note wasn't so bad, after all."

It was a tight squeeze. Jack sat in front with Remedios and one of the bags. Mr. Temple and Bob, both big individuals, filled the rear with the balance of the bags. Frank, who had gone to the front of the car to crank it, found no room within for him when he returned. He leaped to the running board.

Remedios opened the throttle and with a rattle and roar, the ramshackle old car darted ahead on the road taken by Gabby Pete, and soon had left the town behind and was out on the desert.

Only the upper edge of the sun stood now above the western mountains, and the purple shadows were long across the plain. In the east the sky was darkest blue and the stars already twinkled brightly. A rosy light lingered at the zenith, while above the western mountains the sky was ruddy bright with the afterglow as the sun slipped farther and farther down and finally vanished altogether. Then night began to descend with a swiftness unknown in the East. The rattle of the car made conversation difficult and the newcomers lapsed into silence, becoming absorbed in watching the majesty of the scene.

Presently the engine began to miss fire, then emitted a final groan as Remedios closed the throttle, cutting off the flow of gas, and stopped. Remedios threw the clutch into neutral, applied the brake, and climbed out. Raising the cover of the hood, he peered within. Then he shook his head dolorously.

"It is of no use, Senor," he said to Frank, who had jumped from the running board and stood beside him. "She is finish. The spark plug, she is on the—what you call it?—the bum." And with an air of finality, he closed the cover. At the same moment he turned to peer anxiously down the road ahead, whence came now on the still twilight the thudding hoofbeats of a galloping horse, rapidly growing louder.

His mechanical instincts awake, however, Frank paid no attention to the approaching horseman. He had again lifted the cover, as Remedios turned away, and, lighted match in one hand, was twisting at a spark plug with the other.

"Shucks," he cried, withdrawing his head, "that Number One plug wasn't screwed in tightly enough, that's all. I'll bet she'll go now, just the way I tightened her by hand. And if I only had a pair of pliers——"

At that moment, the galloping horseman dashed up alongside, pulling his horse back on his haunches. It was Gabby Pete, his hat gone, his face red with excitement. Far over he leaned to call to the astonished occupants of the car.

"Bandits," he cried hoarsely. "Greasers. Comin' in an auto. I come back to warn you." And facing about he pointed to where a cloud of dust behind him on the desert road indicated a rapidly oncoming car.

"Grab that crank," cried Frank to Remedios, and he sprang for the driving wheel. "I'll make this old bus go."

"Not so fast, Senor," said Remedios suavely, and seizing Frank's arm he whirled the young fellow about.

CHAPTER X

A BRUSH WITH THE ENEMY

Remedios seized his shooting wrist in his left hand and danced up and down in the road, while his weapon fell to the ground.

Frank, who a moment before had been gazing into the leveled weapon of the traitorous Mexican chauffeur, whirled about to face his friends in the car.

Smoking revolver in hand, Jack Hampton stood upright in the front seat. It was he who had fired the shot.

"I didn't touch him," cried Jack, "merely shot his revolver from his hand. Jump in Frank, for here come the bandits."

With a rattle and roar the car of the bandits approached, not the length of two city blocks away on the desert trail.

As the Mexican sprang to the crank, and started turning, Frank leaped to the driver's seat of the flivver and manipulated throttle and spark. With a clatter the engine turned over and began to race.

The bandits' car had slowed almost to a stop, four or five lengths away. Frank released the hand brake, pressed the clutch into low with his foot, and shot ahead.

Shifting the clutch into high, Frank opened the throttle wide and the old rattletrap seemed fairly to leap ahead, its wheels spurning the ground. The lights of the other car which had theretofore seemed dimmed were switched to full brightness. Before the blinding glare in his eyes, Frank involuntarily ducked his head.

As his eyes left the road, the car swerved. A shot rang out from the car of the bandits, ripping high and doing no damage.

There was a crash, the flivver lurched, then sped on. As rapidly as possible Frank brought it to a stop and then stood up to look back and view the damage.

Mr. Temple and Bob, in the rear seat, already were on their feet. Jack stood beside Frank, peering into the shadows behind. The moon was in its first quarter, low down and shed only a faint radiance. But even by the wan light, it could be seen that something dire had happened to the car of the bandits. It stood sideways across the road, leaning drunkenly to one side. And to the ears of the boys came groans from a number of dark figures in the road.

Gabby Pete, temporarily forgotten by the boys in the excitement, galloped up, cheerful voiced.

"As neat a trick as ever I see," he cried approvingly to Frank. "You tuk off their hind wheel jest like a knife cuttin' butter. They're tumblin' around in the road, a half dozen of 'em. Hey, look out." And Gabby Pete bent low on his horse as a bullet whistled overhead. Another and another followed, and there were shouts of vengeance, and imprecations.

"They're a-comin' to," cried Gabby Pete, slapping Angel Face on the flank, so that the horse leaped forward with a snort. "I'm on my way." And he disappeared into the darkness.

"We're on our way, too," cried Frank, opening the throttle and pressing down the clutch, as more bullets whistled overhead. "Give 'em a shot, Jack, and everybody stoop down."

Jack fired off his revolver, shooting high purposely. He wanted merely to frighten their pursuers into desisting. Then the car gathered momentum, and was soon out of range. Presently Frank, who had been driving the flivver as fast as it would go, with the result that they were all tossed about while the car lurched precariously over the rutted road, slowed down to a more moderate pace.

"Say, though," cried Frank, suddenly realizing Remedios no longer sprawled on the hood, "we've lost our passenger."

To a query from Frank as to the route to be followed and the distance to camp, Jack made answer that the road lay straight ahead with no laterals cutting into it, and that camp was only a couple of miles beyond.

"Say, Jack," declared Bob with a laugh, "that was some reception committee you got out to meet us."

"Yes," kidded Frank, "what were you aiming to do, anyway? Put on a Wild West thriller for a bunch of tenderfeet fresh from New York?"

Jack laughed. "Tenderfeet, your grandmother," he said. "It looked to me as if the effete Easterners put on the thriller for the bandits."

Relieved at the safe outcome of their adventure, everybody joined in the laugh, and for several minutes the high good humor manifested itself in jokes bandied back and forth. Then a 'dobe ranch house loomed ahead, low-lying, of four or five rooms, a wide, dirt-floored porch along its length, upon which the rooms gave through separate doors. At the rear were a clump of shadowy outbuildings and a corral. To one side and some distance away stood a low frame building and a high, latticed tower with antennae, which the chums recognized with a shout of delight.

Frank drew the car to the porch, and Gabby Pete, at the sound of its approach, opened the door of the kitchen and emerged, big spoon in hand, the lamplight streaming from the room behind him, and savory odors floating out to the hungry boys.

"He does," laughed Jack. "That's the way camp cooks announce food is ready in the cow camps, as I understand it. And Gabby Pete is an old cowman."

CHAPTER XI

JACK CANNOT SLEEP

"Well, now, boys, let's see where we stand," said Mr. Temple, after all had partaken heartily, amid excited but disjointed conversation, of a surprisingly good dinner of pork and beans, boiled potatoes, fresh tomatoes and lettuce, bread pudding and coffee. He pushed back his chair as he spoke, and lighted a cigar.

"First of all," he said, "we have got to consider the kidnapping of Mr. Hampton and decide what shall be done in the matter, what moves we must make. Then there is this series of mysterious happenings, all of which have a bearing on the case, if we can find the solution.

"Here, for instance, is this man Remedios. Evidently he was in league with the Mexican bandits who attacked us, and it was his part of the conspiracy to stage a breakdown so that we could be easily attacked. Now who were the bandits, and what did they want? Were they ordinary robbers after money, or was their object something deeper? Was it part of this plot against our oil interests?"

He paused to puff his cigar into renewed life. All three chums had been listening with eager attention. Now Jack Hampton spoke. Mr. Temple earlier had elaborated for Jack's benefit his theory that a faction of Mexican rebels was responsible for the outrages of which they had been the victims, hoping thereby to embroil Mexico and the United States and thus cause trouble for President Obregon.

"Mr. Temple," said Jack, leaning forward, "I do not believe those bandits were after money. Didn't it strike you all as strange that they were in an auto? Well, it did me. The bandits of the border usually are mounted on horseback. These men, on the contrary, had a high-powered car. No, that attack was due to a carefully laid plan. And do you know what I think their purpose was? It was to capture you."

Bob and Frank, elbows planted on the table, leaned forward surprised. Mr. Temple, however, showed no surprise, but merely looked thoughtful.

"You see," continued Jack, "you are an American of wealth and position. They already have captured father. Now, if they were to capture you, there certainly would be some commotion at Washington, the national capital, that would make trouble for President Obregon of Mexico. Maybe another punitive expedition would be sent into Mexico, like General Pershing led in the time of Carranza, after Villa's raid on Columbus, New Mexico. At least, that's what they expect, I guess."

"But, Jack," demanded Frank, "if you are right in your surmise, then it means that these fellows knew in advance of our coming."

"Sure," said Jack, "Gabby Pete knew. And Rollins, father's assistant. But you met the one, and you know he can be trusted. As for Rollins, I don't know much about him. He's a queer, silent man. Not here tonight, because he left early this morning to see a man on business over here some twenty miles or so. He said he might not return tonight. But I know father trusted him."

"Then, Jack, there is one other thing to be considered," said Bob. "And that is, has anybody among our enemies—for I suppose we can call them that—listened-in when we spoke by radio?"

"Of course," said Jack, "with all these amateur receiving sets in use nowadays it is pretty hard to get absolute secrecy. But, in the first place, since that Washington conference, the government has limited the use of certain wave lengths. Now we are licensed to use an 1,800 metre wave length, and I imagine there are very few—at least in this region—who could 'tap' our conversation. In addition, of course, we used our code in discussing when you would arrive."

"No, you're wrong," said Bob. "You used the code when you telegraphed that your father was kidnapped. But, as I recall it, when we spoke by radio after getting your wire, we all were so excited we never thought of the code."

Frank nodded agreement. "That's right," he said. "But, anyhow, we never thought of making it a secret. Perhaps your cook—this Gabby Pete—said something innocently in town. Or the word got around somehow."

"Yes, I suppose that's the way it happened," said Jack, dismissing the subject. "But the question now is, what are we going to do? Shall we, telephone the county sheriff about this attack on us tonight and about Remedios? And—what shall we do about father?"

Mr. Temple who had been puffing thoughtfully throughout this discussion, his head bowed, now looked up, and shook his head in negation.

"Let's not notify the sheriff," he said. "The minute we bring the authorities into this, we run the danger of letting our whole story become known. Then the end which these mysterious enemies of ours seek will be attained. That is, the government will be drawn into the situation.

"As to your father, Jack," and Mr. Temple paused, "well, we shall have to think the matter over pretty carefully before we undertake to do anything. In the first place, as I have said before, I believe he was captured in order to make trouble between Mexico and the United States. Now, here comes a note from his captors demanding that we pay a ransom of one hundred thousand dollars. How does that fit into my theory?

"Well, if we appeal to Washington and ask our government to demand Mr. Hampton's release, there certainly will be trouble. And that, I believe, is what the enemy counts on us to do. If they really were after a ransom, and had no other object in view, it is likely they would not have asked for so big a sum, and also would not have given us two whole weeks in which to carry out their demands. No, I am convinced they expect us to go to Washington and make trouble. Therefore, that is the one thing we must try to avoid doing."

"But, look here, Mr. Temple," said Jack, impulsively and with just the slightest quiver in his voice, "he's my father."

"Yes, I know, Jack," Mr. Temple said in a sympathetic tone, "and I know what you're thinking of. You're thinking your father is a prisoner and ill-treated. And you're saying to yourself that while we hold back here from appealing to the government, something dreadful may happen to him. Isn't that so?"

Jack gulped unashamedly, and turned his head away. "Something like that," he said, in a muffled voice.

The older man dropped a hand on his shoulder. "Don't worry too much, my boy," he said. "We may appeal to Washington, and let the consequences go hang, if that is the only way to bring back your father. But we don't want to act too hastily. Let's turn in now and get a good night's sleep. Then in the morning we'll decide on something definite."

It had been a long discussion, and Bob and Frank were content to do as Mr. Temple proposed. Jack, perforce, agreed, although the strain of the last few days, which he had carried alone, was beginning to tell on him and he yearned for instant action. He showed the others to their rooms, Bob and Mr. Temple sharing Mr. Hampton's room, and Frank bunking in with Jack himself.

After Frank had undressed and tumbled into bed, so dog-tired, as he said, that he could barely keep his eyes open to see the way to his pillow, Jack went out to stand in the starlight on the porch. After leaning against a pillar some minutes, during which his active brain kept milling endlessly over the details of the past few days, he had an impulse to go over to the radiophone station and talk to the guard, an ex-cowboy, on duty there since the attack by three Mexicans at the time this story opened.

Hands in his pockets, head bowed in thought, he moved across the hard packed sand, his feet making practically no sound.

CHAPTER XII

JACK DISCOVERS A TRAITOR

Two figures stood at the door of the radio station power house. The station was a duplicate of Mr. Hampton's other station on his Long Island estate, earlier described. So engrossed were the two men in whispered conversation that they were unaware of Jack's noiseless approach.

The soft sibilant sound of whispering which came to his ears just as he was about to approach the door roused Jack from his reflections. His suspicions were on the alert because of the happenings of recent days, and he halted. Certain, after standing a moment with every nerve tensed, that he had not been seen, Jack backed cautiously until again around the corner of the building.

Who were the two men? What were they whispering about? Pressing against the side of the building, Jack thought quickly. One of the two must be the night watchman. Perhaps the other was the man who kept guard at the station by day. If he were, thought Jack, then, perhaps, some new danger menaced and the night man had called the day man to help him. This theory also would account for the fact that they were whispering, instead of conversing in normal tones.

So probable did this supposition seem to Jack that he decided to join the men and ask what the danger was. Caution, however, prompted him to reconnoitre by peeping around the corner before stepping into the open. The next moment he was thankful he had done so. For, as he looked, one of the two struck a match and held it in cupped hands to a cigarette, and Jack saw the man was Remedios.

Drawing his head back quickly, Jack leaned against the building, trying to compose his thoughts. What was Remedios doing here? Not many hours before he had foiled the plan of the traitorous Mexican chauffeur to deliver him and his friends to the enemy. Was Tom, the ex-cowboy, on guard at the radio plant, a traitor? Jack could not believe it.

Footsteps were approaching from around the corner. Jack looked around wildly. There was no shelter near enough to which to flee. He whipped out his automatic, flung himself down alongside the wall, and waited.

Two men appeared, but instead of rounding the corner they moved straight ahead. They were in earnest, but low-voiced conversation. They did not see him.

Jack stifled an exclamation. The man with Remedios was Rollins, his father's trusted assistant. So stunned was Jack at the revelation that he did not strain to overhear what they were saying. In a moment they were beyond earshot.

Trembling with rage at this evidence of treachery on the part of Rollins, Jack rose to his feet. He intended to stalk the two conspirators. Then a new idea occurred to him. What were they doing at the radio plant? Perhaps, for reasons of their own, they had damaged it or put it out of commission. He decided to investigate.

Rollins and Remedios were now out of sight toward the front of the ranch house. Perhaps Rollins would have the audacity to take the other into his room, which opened like the other rooms directly upon the porch or gallery. If so, Jack could surprise them later. First, he would investigate at the radio plant.

Walking swiftly, he approached the door of the power house. An electric light shone within. The guard, Tom, jumped up from a chair where he had been sitting, reading, at the sound of Jack's hurried footsteps. His hand reached for the ready revolver at his side, but was withdrawn at sight of his visitor.

"Oh, it's you, Jack," he said, addressing him familiarly, for a warm friendship had sprung up between the two. "I thought it might be a Greaser."

"Tom," said Jack, without any preliminaries, and showing his excitement in his voice and manner, "what was Mr. Rollins doing here? Who was that with him?"

Well enough Jack knew who the stranger was. But good friend though Tom was, Jack wanted to test him. The circumstances certainly were suspicious.

"Didn't see the other feller," Tom answered. "He stayed outside. Mr. Rollins said he was an oil driller. Mr. Rollins went into the station there." Tom motioned to the radio operating room beyond a closed door. "Asked me to throw on the juice so he could use the telephone."

"Excuse me, Tom," said Jack. "But after what I've just seen I don't know whom to trust. Yes, I believe you're true blue, Tom. I'll tell you. But wait a minute."

In as few words as possible he related their adventures that day and the part played by Remedios. Then he added that in Mr. Rollins's companion he had recognized the Mexican chauffeur.

Both stood silent. Suddenly the still night was shattered by a series of racketing explosions. Jack sprang for the door.

"Remedios's flivver," he cried to his companion. "There isn't another car in the world can cough like that."

By the time he had emerged from the radio station the car could be heard shooting away down the desert trail toward Ransome.

"Too late," said Jack, disgustedly. "He's gone. I should have surprised them together."

"Listen, Tom," said he. "Not a word about all this. I think I'll not let Rollins know that I suspect him, but will talk this over first with my friends. And if he comes here to radio again listen to him, and report to me what he says."

"All right," said the big ex-cowboy. Then as a new idea occurred to him, he asked: "But how about tellin' my side pard, Dave? He's on duty days. He oughta know, too."

"I don't know Dave as well as I do you," said Jack. "Certainly he ought to be informed, so that he can be on the watch, too. Can he be trusted?"

"You can count on Dave," said Tom. "We been pardners for years. That bow-legged son o' Satan an' me been through lots o' ruckuses in our time. If there's any shootin' to be done, count us in. You know how I kin shoot."

When Jack reached the house, he found Mr. Temple, Bob and Jack on the front porch in their night-clothes. Rollins was there and had introduced himself. All four were discussing the disappearance of the flivver.

"Where have you been, Jack?" asked Frank. "Why, you haven't undressed. I thought you turned in when I did. But I was so sleepy I never noticed when I tumbled out of bed that you weren't there."

"Oh, I couldn't sleep," he said. "So I came out for a turn in the night air before going to bed."

Jack found lying distasteful, but decided it would not do in this case to tell the whole truth. Fortunately, on leaving the radio station, he had swung about in a circle, so as to approach the house from an almost opposite direction.

"Over there," said Jack, indicating the direction from which he had come. "There's a little rise some distance beyond there, but in this feeble moon-light you can't see much, so I came back. Then I heard the flivver."

"Do you think that fellow Remedios came here himself and drove it off?" asked Frank.

Jack noticed that while Rollins was watching him keenly Mr. Temple, who had not taken part in the conversation, was studying Rollins.

"Oh, it must have been Remedios," Jack said boldly. "Did anybody get close enough to see him? Who came out first? Did you notice, Mr. Rollins? You must have just arrived. I see you are still dressed."

"Yes, I had put my horse up in the corral," said Rollins, calmly, "and was walking over here to the house, when I heard the car. I came around to see who was calling at this late hour, but all I could see was the disappearing car. Of course, I knew nothing of your day's adventures until your friends came out, when we introduced ourselves and explanations followed."

CHAPTER XIII

THE NET IS DRAWN TIGHTER

That obvious lie on Rollins's part gave Jack the final assurance that the man was in the plot against them. Burning with indignation, he wanted to expose Rollins but with an effort of self-control he choked back the hot words and also managed to keep his anger from showing in his face.

But it was an effort. Fortunately the others came to his rescue. Frank began to shiver in his pajamas and called attention to the fact that the night air was chill.

"Yes," said Jack, glad of the change in subject, "no matter how warm the days out here, the nights are always cool. Let's go inside."

All trooped into the living room, which was dining room, too. In the big fireplace they found a wood fire laid by the thoughtful Gabby Pete, ready to be touched off in the morning. The talkative camp cook slept in the bunkhouse some distance away, in the opposite direction from the radio plant. While the others dragged blankets from their beds and returned to the living room, wrapped up in them like Indians, Jack touched a match to the wood and the fire soon was blazing merrily.

Rollins would have excused himself on the plea of fatigue after a long day's ride, but Mr. Temple halted him.

"So long as we are here altogether," he said, "it won't hurt matters, and may help them, to have a little talk."

From his chair in front of the fire, Mr. Temple looked up inquiringly at Rollins, who stood to one side of the fireplace, his face in the shadows. The latter did not speak. Jack thought quickly. Was it wise for Mr. Temple, unaware of Rollins's duplicity, to discuss matters with him? He decided not. He was bending down to throw more wood on the fire and without rising he interposed an objection.

"Mr. Rollins must be pretty tired," he said, glad his face was averted because he feared the scorn in his eyes would betray him. "And we've all had a hard day. Suppose we let the discussion go until tomorrow."

Rollins spoke precipitately, and Jack believed there was a little note of relief in his voice.

"Yes," said he, "that would be better. I am pretty tired, as Jack says. Well, I'll turn in. Good night. I'll see you at breakfast and after that we can have our talk."

Shaking hands with Mr. Temple and throwing curt nods to Bob and Frank, Rollins left the room. A moment later Jack arose and followed swiftly but silently to the door on the gallery. Peering around the doorpost cautiously, he assured himself Rollins had entered his own room, then returned.

The others looked at him in surprise, unable to understand the meaning of his actions. Jack soon enlightened them.

Crouched before the fire and with his eyes on the door for signs of interruption, while the others pulled their chairs close about him, Jack in a low voice outlined his experiences of the night.

"No," said he. "All Rollins had to do to spread that information was to tell Remedios. The latter could notify the men who laid for us."

Jack again arose and moved to the door and peered out. No signs of life. He returned and resuming his position said in a low voice:

"That's what I've been asking myself. I've thought it over and I believe I've found the answer. Either he was radioing to the Calomares ranch in Old Mexico where father probably is held a prisoner, or else he was sending a message to the fellows who stole our airplane."

"The big stiff," he muttered. "I'll go get him now and we'll choke it out of him."

"Don't blame you, Bob," said Jack, grinning. "It's what I wanted to do myself. But I believe there is more to be gained by watching Rollins—at least until we have more to go on."

"Probably," said Frank, "if we put it up to him now, he'd be able to lie out of it."

"But he couldn't lie out of being seen with Remedios," said Bob. "Or of using the radio."

"Frank is right, though," declared Jack. "Rollins would frame some alibi, and all we'd succeed in doing would be to put him on his guard."

"Jack is probably correct in his surmise as to who Rollins was calling by radio," he said. "Probably this Calomares ranch is headquarters for the Mexican rebels who are making trouble for us. If it was the ranch that Rollins called, he may have been making his report on today's proceedings. But if he was calling the airplane, that is a more serious matter. It may mean trouble for us tonight, perhaps another attack."

"Great guns," grumbled Bob, "don't these birds ever sleep? Well, believe me, if the Heinie that stole my airplane comes around where I can get my hands on him, I'll fix him."

"I wouldn't do a thing to him, either," said Frank. "Except I'd turn his Kaiser mustaches down so hard they'd never point up again."

"Well, fellows," said Jack, "We have got to sleep. So I propose that we stand guard turn about tonight. It's pretty late now, midnight or thereabouts, so that if we stand two hour watches, the three of us, we'll pull through nicely without spoiling Mr. Temple's slumber."

The older man protested he was as able to stand a watch as any of them, but the boys wouldn't have it so. Finally it was agreed that Jack should take the first watch of two hours, Bob would succeed him and Frank would have the last watch. The man keeping watch would sit inside his bedroom door opening on to the gallery, with Jack's revolver. As the bedrooms adjoined, while that of Rollins was the last in the house, it would be easy enough to guard both.

It had been agreed beforehand that after the expiration of Frank's watch at 6 o'clock there would be no necessity for keeping further watch. Gabby Pete would be up and busy at his early morning tasks, and the oil drillers housed in the bunkhouse also would be stirring about. Therefore, after barring the door, a precaution Bob also had taken in the room shared with his father, he turned in without awaking Jack.

Worn out by their trip of the day before with its attack and the excitement of the night, all slept soundly, and Gabby Pete did not get them up. It was almost 10 o'clock when Jack awoke. He called the others, and soon all were dressed and ready for what the day would bring forth.

Jack was the first dressed. He found Gabby Pete in the kitchen, peeling potatoes, and asked if they could have breakfast.

"Sure thing," said Gabby Pete. "Have it fur you right away. Nice fresh aigs an' ham an' coffee. How's that?"

"Yeah. Give him breakfast early. He lef word he hadda go over to Number Two well where they're still drillin' an' hain't struck oil yet, but said as how he'd be back later today. He tuk them two drillers from the bunkhouse with him."

"Did you know Remedios sneaked up last night and took his flivver again, right from under our noses?" Jack inquired.

Gabby Pete jumped up, almost upsetting his pan in his haste, and called to Jack to wait. Wiping his wet hands on a big blue apron that looked incongruous on the old cowman, he pulled open a drawer in a kitchen table and took out a flat blue envelope which he handed to Jack.

"Almost forgot this," he said. "Your tellin' me about that there scoundrel of a Greaser put everything else out o' my mind. Must be gittin old an' forgetful. One o' these days I'll forgit my head."

He would have rambled on garrulously, but Jack interrupted. He turned the envelope over curiously. It bore no address or writing of any kind, and was sealed.

"Oh, that's somethin' Mr. Rollins musta dropped out o' his pocket at breakfast. Found it on the floor beside his chair after he was gone. Will you give it to him?"

"Have we any right to open this?" he said, after explaining how he had obtained the envelope. "I for one believe that we should. It may contain valuable information to us."

"You're right, Jack," said Mr. Temple. "I'm a partner in this oil enterprise, and if one of our trusted employees is a scoundrel we are entitled to know it. Give me the envelope. I'll take the responsibility."

While the others looked on, Mr. Temple ran a knife along the edge and slit the envelope open. Inside was a mass of documents and a letter. Mr. Temple unfolded them, gave one look, then with an exclamation jumped to his feet.

CHAPTER XIV

THE KEY TO THE MYSTERY

The three boys crowded around Mr. Temple, who in one hand held the mass of documents and in the other the letter. He was reading the latter.

"Boys," said he, "this proves Rollins's complicity in a plot against us. But it makes matters more puzzling and complicated, too."

"Well, first of all," said Mr. Temple, holding up the thick sheaf of papers, "this is Mr. Hampton's own original list of the leases secured by the group of independent oil operators to which I belong and which he represents here in the field."

"Is it a copy of the list I recovered from the thief who stole it from Mr. Hampton's house on Long Island?" asked Bob.

"No," smiled Mr. Temple. "It is the original. That was the copy. And this letter with it is one written by Rollins to a man in New York City who is one of the minor officials of the Oil Trust. It is too long to read to you. But from it I gather that Rollins is a spy in the employ of this official."

"Say, Dad," declared Bob, "this is too much for me. If the Octopus is responsible for our troubles, then where do the Mexicans come in? And vice versa?"

"That's what I had in mind, Bob, when I said this discovery complicated matters," said Mr. Temple.

"Sh," warned Jack, from the window toward which he was glancing at that moment. He sprang forward to see better. "Here comes Mr. Rollins now. And in a tearing hurry, too."

Rollins jumped from his horse and ran along the porch to his room. They heard the door slam, and then sounds of a furious searching being carried on. The boys and Mr. Temple, gathered around the door and window, looked at each other significantly.

A moment later Rollins called for Gabby Pete from the door of his room. The cook hurried to him from the kitchen.

"Pete, did I drop an envelope—a long blue envelope—at breakfast?" asked Rollins, making no attempt to conceal his anxiety.

Rollins complied. When he saw Mr. Temple, Bob and Frank, he recoiled as if to flee. But Jack barred the doorway. Rollins was speechless. Mr. Temple advanced, holding out the document and the letter.

"Your duplicity is discovered, Rollins," he said. "I make no apology for having opened your sealed envelope, because last night Jack Hampton discovered you at the radio station with Remedios, and we knew you were faithless to your trust. Come, make a clean breast of it."

Rollins seemed to shrink and grow older before their eyes. Suddenly he sank into a chair. His shoulders sagged. Pressing his hands to his eyes, he bent forward and began to cry. Not the noisy crying of a child but great, dry, wrenching sobs.

The older man nodded approval and the three boys filed out, closing the door behind them. Simultaneously each drew a long breath of relief. Bob was the first to speak.

At that moment, Gabby Pete poked his head from the doorway of the kitchen. Seeing the boys, he called:

The three started on the run for the dining room, their youthful spirits rebounding from the depressing scene in the room they had just quit in answer to the tang of a perfect day and the cook's breakfast call. Bob suddenly halted with an exclamation.

"Oh, he's too busy to miss his breakfast," said Frank. "Anyhow, we can get the cook to put up something for him."

They ate hungrily with little conversation. Pete hovered near and his presence restrained them from talking about the topic that was uppermost in their minds.

"How about taking a look at the radio plant?" asked Jack when they had ended breakfast.

The others agreed eagerly. They were in the act of leaving the table when Mr. Temple appeared. They crowded about him with questions.

"Easy, easy there," he protested. "I'm hungry as a hunter. Suppose you boys wait outside for me while I get a bite, and then I'll join you."

When Mr. Temple emerged, he lighted a cigar and leaned against a pillar. The boys stood about him. For several moments he was silent, staring out over the expanse of desert to the hills beyond, all shimmering beneath the heat of the summer sun.

"It's a long story," he began, "but I'll simplify it for you. Rollins held the key to the mystery. He has a family back East, an invalid wife, a son in college, a daughter just preparing to enter college. All that takes money, for doctor bills and school bills and clothes for the girl. Rollins was a poor man on a salary.

"He needed money and couldn't see his way to getting it. Then a minor official of the Octopus put temptation in his way by making him a proposition. Mind you, he wasn't one of the big men of the Oil Trust. I feel certain they know nothing about all this.

"This man proposed that Rollins obtain certain inside information about the independent oil operators and sell it to him. Rollins wanted to, but couldn't get the information. It was too closely guarded by Mr. Hampton.

"It was then that another temptation came Rollins's way." Mr. Temple paused. "A weak man seems to carry certain earmarks that draw scoundrels to him, boys," he said. "It was so with Rollins. At this moment a representative of Calomares, the Mexican landowner who is backing the northern rebels, sought him out with a proposition that he betray his employers. The rebels, as I suspected, wanted to make trouble for President Obregon, of Mexico, by embroiling him with the United States. And the way they wanted to set about it was by raiding the independent oil operators. They needed a spy at our headquarters, and they proposed that Rollins should become their man.

"Then Rollins had an inspiration. He told the Mexicans that if they would help him, he would aid them. It was agreed. The agent who had acted for Calomares in the negotiations was this German, Von Arnheim, an aviator and a German secret agent in Mexico during the war. He took the man Morales with him to Mr. Hampton's Long Island home to steal the duplicate list of independent leases and other data which Rollins had learned was kept there."

"Yes," said his father, "and it was because you foiled them that Rollins came into possession of Mr. Hampton's own original copy of the list and other data. For he stole it from Mr. Hampton's effects after Von Arnheim and Morales had carried him away captive in our airplane."

"As you suspected, it was for the purpose of capturing me, too," said Mr. Temple. "And Rollins had let the bandits know when I would arrive. Remedios was his go-between."

"I found that out, too," said Mr. Temple. "He was talking to the Calomares ranch in Old Mexico, which has a very powerful station, according to Rollins. He says the German, Von Arnheim, told him that there are similar powerful radio stations scattered throughout Mexico and South America, all built by German money for the use of its spy system. And he said this German told him the most powerful station of all was on an island in the Caribbean, and that it was so powerful it could communicate with Nauen, Germany."

It was apparent that Mr. Temple had concluded his explanation, and Bob and Frank began to ply him with questions. Jack, however, stood silent, his face averted. Mr. Temple presently broke from the others and laying a hand on Jack's shoulder whirled him about.

"Well, Jack, I've got the beginnings of a plan in mind. But first I must get more information from Rollins. Then I'll talk to you again."

"Mr. Temple," said he firmly, "I'm desperate. Father is everything in the world to me. I'll wait to talk with you. But I tell you frankly the only plan that appeals to me is to ride into Old Mexico and rescue him."

The eyes of Bob and Frank, who had turned to listen, lighted up, and they nodded vigorous approval. Mr. Temple stood off and looked at the trio of husky fellows as if seeing them for the first time.

CHAPTER XV

TO THE RESCUE

"I may be wrong," said Mr. Temple, thoughtfully, "in giving my sanction to this plan to rescue Mr. Hampton. But I do not believe so. And, all things considered, it seems the best if not the only way out.

"I have been accustomed to regard you as mere boys, but the conduct of every one of you in our adventures lately shows me you are able to think and act for yourselves. Yet I don't know. Jack, you and Frank are motherless. But—if anything happened to Bob—his mother never would forgive me."

"Say, Dad, forget it," grumbled the big fellow to hide his emotion. "I can take care of myself."

"Yes, I guess you can," he said. "And you carry a cool head, too. At any rate, I've given my approval."

He smiled whimsically, then looked from one to another of the three eager young fellows.

"My daughter Delia was right," he said. "When I left home she said I was wrong to think of you any more as youngsters, and that the first thing I knew you would be making use of your wit and ingenuity to take care of me. And now her words in a measure are coming true."

All four were grouped around the dining room table. For several hours plans for the rescue of Mr. Hampton had been discussed and rejected. Out of it had grown a plan which called for a daring invasion of the enemy's territory by the boys.

Mr. Temple had impressed upon them the necessity for preventing the United States government from being involved in the situation. He had explained a number of angles not made clear before. Among other considerations, he said, was the fact that practically all the Central and South American republics were jealous of their big Yankee neighbor.

"If our government were to make a hostile move toward Mexico," he declared, "the other Latin republics would misconstrue our motives. They would consider that because of our size we were acting the part of the bully in order to reap financial benefit. They call us the 'Dollar Republic,' you know. Our interests in Central and South America would suffer a severe setback."

Accordingly, it was distinctly up to the boys and Mr. Temple to effect Mr. Hampton's rescue themselves. And out of the discussion had grown the plan to have Jack, Bob and Frank make their way to the Calomares ranch and offer their services to the rebel forces in the guise of young Americans who were seeking adventure.

Once within the rebel stronghold they would bide their time and await an opportunity to free Mr. Hampton and escape with him.

"I, for one, won't be content until I get back our airplane," said Frank, when the details were being discussed. "Probably we shall be able to recapture it, and then we can all four make our escape in it. The 'plane carries three easily and can be made to carry four at a pinch."

Jack said he was certain enlistment in the rebel forces would offer no difficulties. From Tom Bodine, the guard at the radio plant, with whom he had had many conversations during the past two months about conditions on the border, he had learned that adventurous young Americans fought frequently on one side or another in the Mexican revolutions.

"I can speak Spanish pretty well, too," Jack pointed out. "And Bob and Frank have a smattering of the language, which they picked up from me."

It was true. Two years before Jack had spent his summer vacation in Peru where his father was engaged at the time in inspecting mining properties. Jack had learned considerable Spanish during his stay and on his return home had continued his studies of the language. Moreover, he had aroused the interest of his chums to such an extent that they also had begun to study Spanish. Often, when by themselves, the three boys spoke to each other in the language. Spanish, by the way, is the easiest of all foreign tongues to learn, as, unlike French and Italian, all letters are sounded, and the grammar is very simple.

Mr. Temple was not to accompany the boys because, in the first place, his age and distinguished appearance would arouse suspicion. Young fellows riding in to enlist in the rebel forces was something that could be understood. But in his case it would be a different matter.

He would stay at the ranch with Rollins, whom he decided to give another chance. Rollins knew the business details of the oil operations and unless he were retained the work could not go on. For that reason, and also because he believed Rollins was truly repentant for his treachery and would be faithful in the future, Mr. Temple retained him.

Rollins had supplied valuable information for the expedition. He gave the exact location of the Calomares ranch, in a valley amid low mountains more than one hundred miles to the south.

There were two possibilities that the boys might be recognized for what they were: if Remedios should arrive at rebel headquarters, or if Von Arnheim or Morales recognized Bob as the youth who had foiled them on Long Island. Neither was very likely. Remedios, they learned from Rollins, had no intention of leaving the district because even if the boys tried to cause his arrest he had a mysterious political pull with the American officials, practically all of whom were of Mexican descent. As for Morales and Von Arnheim they had had only a fleeting glimpse of Bob and he could disguise his appearance sufficiently to make that of no account.

"Well, boys," said Mr. Temple finally, "if we all were back in New York under normal conditions I should consider this just about the craziest notion ever, and never would consent to your carrying it out. But out here, amid these changed surroundings, it seems the natural thing to do. For the life of me I can't bring myself to feel any alarm."

It was now late afternoon. Tom Bodine was to escort the boys to the border as soon as darkness fell, making a big swing around Ransome, so as to avoid notice, and set them on their way. They would travel by horseback, all three having ridden since childhood. There were a number of good mounts in the corral from which to select.

The boys planned to ride the major portion of the night until they should reach a cave in the first of the Mexican foothills, where they would spend the next day in hiding. Tom Bodine knew the cave of old and was able to give the boys the location of certain landmarks which would make it easy for them to find it. The following night they would continue their journey, and this should bring them to the Calomares ranch on the morning of the second day.

"Time to get ready," said Mr. Temple, looking at his watch. "And, remember, the very first thing you must try to do is to get into their radio station and call me. Day or night, the men here will be watching for your signal and will call me. I'll be mighty anxious about you. So remember."

"We shall call you, sir," said Jack, as the boys moved away. "And don't worry. I'm sure we'll come out all right."

CHAPTER XVI

"I will that. An' if it's in trouble you are, Dave an' me'll be ridin' just as fast as we can to help you. Wish you'd let me go 'long. I'm half minded to follow you."

"No, no. We'll stand our best chance alone. They won't suspect we're other than a bunch of wild young fellows out for adventure."

Tom grumbled, but the force of the reasoning was apparent to him. They leaned from their horses for a last firm handclasp, then Jack rode on to join Bob and Frank who sat on their horses some distance ahead.

"You're the boy to give it to 'em, Jack," called the big ex-cowboy in a last farewell. "Give 'em thunder."

Jack waved a parting salute as he joined his comrades. Frank and Bob did likewise. Then with night settling down over the vast desert waste they rode on into old Mexico.

Beside the white stone marking the international boundary, Tom Bodine sat his horse like a statue. Moodily he watched until they were out of sight. It was a hard life Tom had led in his day and when he took the job at the radio plant it was with a sigh of relief at the ease ahead of him. But now despite his fifty years, the last thirty of which had been filled with hard knocks, he felt the old call to adventure urging him on.

With drooping head, he turned his horse toward home. But hardly had the animal started forward, than he dragged it about again.

"Let's go," he shouted to the empty silence, and whirling his sombrero aloft, brought it down on his horse's flank. Then he rode on after the three figures that had been swallowed up in the darkness.

Far ahead of him, for Tom had taken considerable time to reach his decision, rode the three companions. The young moon shed only a wan and wraithlike radiance over the plain. They were alone, and the parting with their last friend, combined with the solitude of the open spaces, had its effect upon them. They rode awhile in subdued silence. But not for long. Frank's lively spirits were the first to rebound.

"Race you to that rock," he cried, pointing to a solitary outcropping of rock, about twice a man's height, about a quarter of a mile ahead.

With a shout that shattered the silence as if a band of wild Indians were hitting the trail, the three boys dashed away.

Presently they pulled up by the rock, practically neck and neck. Their eyes were alight now with the zest of adventure.

"Well, for one thing, we must save our horses as much as possible. We already have come twenty miles, and we have thirty miles more to go before reaching Tom's cave."

A martial trio they made. Jack was clothed in the khaki shirt, riding breeches, high laced leather boots and sombrero in which he had met the boys on their arrival at Ransome. Bob and Frank were similarly outfitted. Tom Bodine was about of Bob's proportions, and his partner Dave Morningstar had the build of the slighter Frank. These two old cow punchers had given the boys the run of their wardrobes. Each lad carried an automatic at his hip swinging from a well-filled cartridge belt. In addition, Jack bore his repeating rifle in a leather scabbard on his saddle.

Frank cast an appraising eye over himself and his comrades, and grinned with approval. Despite Jack's rebuke, he could not long keep silence.

"Well, here we go, fellows," he said cheerfully, "just like the Three Musketeers. Jack with your air of melancholy you can be Athos. Bob is big enough to be Porthos, although I have got his appetite. I'm Aramis."

"Aramis was always dreaming about the ladies," said Bob slily. "Heard from Della lately?"

Frank was silent a moment under the sly dig, his thoughts flying back to the faraway Long Island home. But his irrepressible spirits would not permit him to remain silent for long, and soon he burst forth again.

"All we need to make it complete," he said, "is D'Artagnan. I wonder if we'll find him."

Jack made no answer. His thoughts were busy turning over plans for the rescue of his father. Bob, too, was unusually silent, thinking of the parting from his own father and the latter's anxiety which almost had prevented his making this venture. Frank pursed his lips to whistle, thought better of it, and jogged along as silent as his companions.

So they rode hour after hour, only the creak of leather, the occasional stumble of a horse or the distant call of a coyote breaking the stillness. At length a low range of foothills, upflung before them, began to take shape out of the darkness with their near approach. Presently Jack called a halt.

It was in the early hours before dawn, when the darkness if anything becomes more intense. A chill nipping wind long since had caused the boys to unroll the rubber ponchos strapped to the back of their saddles, and drape them over their shoulders. As they stood now in the eerie darkness, striving vainly to locate the landmarks of tree and rock which Tom had given them, the howl of a hunting coyote floated down the wind. The sensitive Frank shivered.

"I'm scared stiff," averred Frank. "My hair is standing up so straight I wonder how my sombrero stays on."

They grinned affectionately at each other. Jack who meantime had been investigating, turned with a worried expression.

"I've followed Tom's directions faithfully," he said. "He said to lay our course south by south-west and showed me what he meant on my compass. I haven't deviated a hair's breadth. Somewhere about here should be the first landmark—three rocks shaped like a camel lying down. But I can't see them."

"Nothing to worry about in that," said Frank. "Probably we haven't gone far enough. Let's push on."

"Keep your guns handy," whispered Jack. Whenever the three were together he took command. "Don't fire without cause, however," he whispered. "If there is someone behind us, it may be another traveller."

Again came the sound of a horse stumbling. All heard it distinctly. Jack peered into the darkness and called firmly:

"The same," replied the ex-cowboy, materializing out of the darkness, and approaching. "And glad I am," he added, "to find you."

"But, good gracious, Tom, is anything the matter? Why are you here? I thought we left you heading back for home five hours ago?"

"No, you just left me," said Tom. "That's all. I didn't head home, because I wanted to come along. Been a-trailin' you all the way. And here I am."

Jack was surprised, indeed. But now that Tom was with them, he experienced a sense of relief. To venture into a strange land without a guide, and in pitch darkness, besides, was a pretty stiff undertaking. The responsibility of looking after his friends was no light one.

"I had just about decided when you came up," Jack added, "that I had lost my way. Frank thought, however, we merely hadn't gone far enough to find your landmarks."

"He was right," said Tom. "You come straight as a die. All we got to do is to ride on a piece an' we'll be in the snuggest cave ever you see."

Riding two abreast, Tom and Jack in the lead and Frank and Bob close behind, they pressed on another twenty minutes when Tom called a halt to indicate a clump of rocks close at hand which suggested in their outline a crouching camel. Then he led the way toward the left.

"Wait, wait," called Bob, in a tense voice that reached the ears of all, and caused them to halt. "Keep your horses quiet and listen. There. I was right."

All sat silent, and distinctly there came to their ears the hum of an approaching airplane.

CHAPTER XVII

INSIDE THE CAVE

"What is it?" whispered Tom Bodine, to whom the sound was unfamiliar. "Sounds like machinery of some kind."

"Airplane? An airplane?" said Bob, low voiced. "It's better than that. It's our airplane, if I know anything."

"They've shut off the motor," said Jack. "They must be going to land. But where in the world could they land in these hills and in this darkness, too?"

"Why, there's a big level place just below the cave I was tellin' you 'bout. A plateau. Smooth as a floor."

The hum of the airplane had died away. The boys and their guide never had caught sight of the machine in the darkness.

Suddenly Frank pointed in the direction whence the sound of the airplane had come, ahead and slightly to the left.

"I thought I saw a light there," he whispered. "It was just a faint streak of orange. Now it's gone."

"Look here," said Bob to Tom Bodine, "does that cave face this way or is it on the other side of a hill?"

"Well, I'll bet you there's somebody in that cave. And the light that Frank saw was some kind of a signal to the airplane."

"Mebbe you're right," he said doubtfully. "I don't know 'bout such things. But who'da thought that cave would be discovered. Why, I just come on it accidental like onct when I was wanderin' through these hills."

"Boys, there's only one thing to do," said Jack in a determined voice, "and that's to investigate."

"Righto, Jack," said Frank eagerly. "Here's our chance to get back our airplane."

"Not so fast," said Jack. "First we must have a plan of campaign. Tom, what's the lay of the land? How far away is the cave? Would it be better to leave our horses here and approach on foot?"

"Cave's not more'n half a mile from here," answered Tom. "It's just around the shoulder o' this hill we're on right now and near the top. I tole you 'bout that big rock in front o' the entrance an' them three lonesome trees at the foot that give you a bee-line to the rock. Well, we can git to them trees without bein' noticed an' tie our horses there an' then sneak up afoot."

"Only one," answered Tom. "There's a kind o' chimney up through the rock to the top o' the hill. But nobody couldn't git out there in much of a hurry. We won't have to worry 'bout that."

"How far would those fellows in the airplane have to go to reach the cave after landing?"

"Maybe we can cut them off before they enter the cave," said Frank. "They'll be busy about the airplane for several minutes before they start to make their way to the cave. How would they have to approach the cave?"

"Well, if we hurry," Frank declared excitedly, "maybe we can capture them before they reach the cave."

"Right you are, young feller," approved Tom. "But we'll have to leave our horses behind or they might give us away. We can't tie 'em to those trees like we planned."

"We can't hobble them," said Jack, thinking quickly, "because they would wander aside a little distance, anyway. And we may want them again in a hurry."

"Tell you what," said Tom, "seems like I remember a clump o' trees just this side o' them three I spoke about. We can tie 'em there. An' them fellers in the machine won't have no horses, so ours ain't likely to nicker."

Presently at a low-spoken word from the guide the boys dismounted and tied up their horses. Then, Jack carrying his rifle, and the others following close at his heels, revolvers in hand, they pressed on toward the three trees forming Tom Bodine's landmark.

As they reached the trees, low exclamations burst from the boys. Hitherto, they had been cut off from the plateau by the shoulder of the hill. Now it lay below and before them. This of itself would not have permitted them to see, as the darkness was intense. But now the scene was illuminated by a number of oil flares stuck upright in the ground in a rude circle.

And right in the middle of the circle was the airplane stolen from Bob and Frank. There could be no mistaking the all-metal body nor the peculiar wing spread, even at that distance of close to half a mile.

Several figures were moving about. As the boys looked on, these seized oil flares and started moving toward them.

"The two men in the airplane and the man in charge of the cave," said Jack. "Dollars to doughnuts, the cave is undefended right this minute. What do you say to capturing it and laying for them there?"

All four were grouped together, and consequently all heard Jack's proposal. Bob and Tom Bodine agreed eagerly.

"Lead the way, then, Tom," said Jack, "because you know the route. And be quick."

Swiftly, yet withal cautiously, because the cave might be defended, they approached the big rock. As they sidled around it, a gleam of light from the mouth of the cave at the rear of the rock fell athwart their path. Involuntarily they drew back.

Then Jack brushed Tom Bodine aside and took the lead. His repeater thrust before him, crouching, he entered the mouth of the cave. A moment later his whisper came back:

A hasty glance around revealed the first of the two chambers, which Tom had said the cave possessed, was luxuriously furnished and lighted by a powerful electric bulb enclosed in a huge frosted globe suspended from the middle of the roof. There was no time for further investigation because Jack already was pushing on toward the heavy hangings at the rear covering the mouth of the second chamber, and the others clung to his heels.

Parting the hangings quickly, Jack threw his rifle to his shoulder. Then he and his companions received their second big surprise. The room was empty of human occupants. But it, too, was brilliantly lighted.

To the trained eyes of the boys that much was apparent at first glance. In one corner of the tremendous cave hummed the dynamo. From it, of course, came also the electricity for the lights. Before they could pursue their investigations, however, Tom Bodine, who had dropped back to the outer entrance, issued a warning hiss. Then he darted across the outer room and joined them.

"Good," said Jack, taking command. "We'll give them a surprise. These hangings are fastened to rings on a big pole up above us there, and they'll slide easily. Tom, you and Bob grab the hangings in the middle and be ready to pull them aside when I say the word. Frank, you and I will stand here in the middle and keep them covered."

All took their assigned positions as the sound of voices was heard at the outer entrance. Jack peered between the two folds of the hangings and smiled with satisfaction.

CHAPTER XVIII

THE FIGHT IN THE CAVE

Tom and Bob, the hangings disposed of, ranged themselves on either side of the pair. Four weapons covered the group in the outer room.

The three men, who had advanced well to the center of the room, stared dumbfounded at these apparitions. Then amazement gave place to anger, and one of the trio made a move as if to draw his revolver.

Three pairs of hands were unwillingly elevated. Two of the men wore sheepskin jackets and leather helmets and the boys surmised correctly that they had been up in the airplane. Bob felt certain they were Morales and Von Arnheim, the two who had made the trip to the East to steal Mr. Hampton's papers and whom he had foiled in that purpose, but who had succeeded in stealing the airplane and making their way to Mexico in it. The other was a rangy man of about twenty-six, keen and shrewd-looking, and had the appearance of an American. Evidently he was the guardian of the cave. And it was he who had moved to draw his weapon when surprised. A tough customer and one to be watched, thought the boys.

With weapons held ready, the three boys advanced. At that moment, the caretaker of the cave took one step forward and instantly the lights in both rooms faded out and the cave was in inky darkness.

The boys were so taken by surprise that for a moment they did not fire. Neither did Tom, for fear of hitting them as they were in front of him. This gave their three enemies an opportunity to shift position and fling themselves prone.

When after their surprise, the boys did fire, their bullets merely pinged against the distant wall and did no damage. But the flash of their weapons betrayed their positions and answering bullets came uncomfortably close. One swept Jack's hat from his head.

From behind them Tom Bodine's revolver spoke, as the enemy thus betrayed themselves. The soft thud of a bullet striking flesh, a groan, choked off in the middle, a hasty scrambling to get away from the danger point on the part of the man struck, then silence.

This silence was so profound the boys seemed to hear the beating of their own hearts, and tried to hold their breath for fear of betrayal. They had thrown themselves prone after the first volley and lay so close they were touching, Jack in the middle.

Each side was fearful now of firing at the other, lest the flashes give their position and an answering bullet find its mark.

Jack thought quickly. Putting his lips to the ear of each of his companions in turn, he whispered:

Each signified by the pressure of a hand that he understood. Certainly it would not do to have the enemy escape and thus cut them off in the cave!

Slowly, carefully, noiselessly, Jack wormed his way to the rear and when he considered he must be in Tom Bodine's neighborhood he began whispering in a tone that could not be heard more than three feet away:

Running a hand over Tom Bodine's body, Jack found his ear and, as he had done with Bob and Frank, set his lips to it. He explained his purpose to gain the entrance to the cave and prevent being bottled up. Tom nodded approval, and Jack was about to return to his companions when he suddenly thought of the radio room beyond, and its possibilities. It would never do to leave that unguarded. Their enemies could telephone the Calomares ranch. Then, even if the boys escaped, their identities would have become known at rebel headquarters. Their chances of rescuing Mr. Hampton would go glimmering.

"That's right," whispered Tom in return. "Tell you what. I'll guard this here inner room from behind the rocks in this doorway. You three stop up the outer entrance, an' well have 'em bottled."

Jack made his way back to his comrades, and the three started crawling. They moved inch by inch, so as to avoid bumping into furniture—a number of heavy chairs had been seen standing about the great room.

Jack was in the lead, Frank at his heels, Bob bringing up the rear. Cautiously, tortuously, they made their way ahead for what seemed like ages, pausing frequently to listen.

After one such pause, as he again started to follow Frank, Bob felt a form brush against him from the side. Then an arm shot out and encircled his neck. Bob wriggled about to face his opponent and threw both arms about him in a mighty clasp.

As they fell to the floor, Bob heard a strangled cry from Frank and a grunt from Jack. They, too, had come to grips with the enemy. Their three opponents had started for the door with the same purpose held by the boys—that of bottling up the other side. The two crawling trios had brushed against each other in the middle of the floor.

Now three individual fights raged furiously on the floor of the cave in Stygian darkness. Every man fought for his very life. The sob of labored breathing was the only sound—that and the threshing about of bodies.

Tom Bodine was sick with rage at his helplessness, for he dared not shoot lest he hit one of the boys, and he could not see to take a hand. He decided to try to find that button in the middle of the floor of the outer cave which the enemy had used to throw off the lights. If not that, perhaps there was a wall switch somewhere. In his pockets was a box of safety matches. With these in his hands he started for what he thought was the middle of the room.

Recklessly Tom struck and lighted matches, searching the floor for that button, stopping after each match burned down to his fingers to listen to the panting, heaving struggle going on about him.

At last he found the button and pressed it. Light once more flooded both caves, dazzling to the eye after the pitch darkness of the moment before. Jack and Frank were still tightly locked with their respective foemen. But at the very moment the lights were switched on, Bob got the upper hand of his man with a famous hold he had used to advantage in winning his wrestling fame at school. There was a heave, and then Bob straightened up and the other went hurtling through the air. He was the American of the enemy trio.

The man fell on his left side, a yard or more away, by a quick twist avoiding the descent on his head, which is the usual result of such a wrestling toss. His right arm was outflung and, as he skidded along the floor, the fingers of his right hand came in contact with a revolver dropped by one of the wrestlers.

Twisting about like a cat, with a convulsive movement, the man came to his knees and fired. There was a warning shout to Bob from Tom Bodine. But the man's aim was far from steady, and the shot went wide.

Bob leaped forward as if shot from a catapult, letting out a wild yell as he did so. It was a tremendous leap from a standing position, and he descended feet first on the other before he could discharge the revolver again. Beneath the impact of Bob's weight the man went down like a shot rabbit and lay still. Bob disarmed him, turned him on his face, pulled his arms behind him and began tying them with his belt.

Meantime Jack was getting the better of his man, the Mexican. But Frank, slightest of the three boys, was putting up a losing fight against the German. The latter had him down and was kneeling on his chest with his hands throttling the boy. Frank's face was purple and the breath was whistling in his throat, while his efforts to throw the other off were becoming more and more feeble.

Tom Bodine took in the situation and sprang forward, clubbing his revolver. He brought it down on the German's head. There was a sickening thud. One blow was enough. The German's hands relaxed their grip on Frank's throat, and he rolled over unconscious.

At the same moment Jack pinioned the arms of the Mexican, and the latter lay helpless.

CHAPTER XIX

RESTING UP

Swiftly Tom Bodine trussed up the unconscious German with the man's own belt, while Jack similarly treated the thoroughly cowed Mexican, Morales. Meanwhile, Bob went to Frank's aid, assisting him to a chair, bringing him water from a spring in a corner of the inner cave and fanning him with his sombrero.

None of the three boys had suffered more serious injuries than bruises, but Frank had been badly battered in the encounter with his heavier opponent and the muscles of his left shoulder had been severely strained.

Despite the mauling he had received, Frank wanted to go and inspect his beloved airplane at once and Bob, the co-owner with him, was equally eager. Jack, however, protested.

"No, sir," said he firmly, "you are in no condition to go chasing off down this rocky slope. The airplane isn't going to fly away. It's in a pocket in the hills that nobody is going to discover. And, anyhow, there is nobody around in this desert place to do any discovering.

"Moreover," he continued, "it is almost morning now. We all have been riding all night and with this fight coming on top of everything else, we are thoroughly tired out. So, instead of any more conversation tonight, I propose that we turn in and go to sleep, leaving one man on guard. At the end of two hours he can call another fellow, and in that way we can all get four or five hours sleep. I'll take the first watch and—"

At that moment a groan from one of the prisoners on the other side of the room interrupted, and with an exclamation Bob started forward.

"Good gracious," he said, "I'd forgotten all about that chap. His arm felt wet and sticky when we were wrestling and I believe he's the man Tom wounded with that first shot in the darkness."

Bending over his late opponent, Bob noted a dark brown stain on the left shoulder of his coat.

"Only a flesh wound, I reckon," said the other. "But it sure hurts. Are you going to leave me like this?"

"Of course not," he said. "What do you think I am? Here, let me help you up and we'll have a look at it."

Bob assisted the other to a chair. His hands were then untied, the coat sleeve cut away and an examination made of his injury. It proved not serious. The man told Bob where to find a bottle of iodine. He winced under the sting of its application, but made no outcry. Then a rough bandage was made of clean handkerchiefs, and the boys stood back to examine their handiwork, for all had taken part in the operation.

"You're some fighter, kid," the other said approvingly to Bob. "But I reckon I'da got you at that if it hadn't been for that arm."

"You're an American, aren't you?" asked Frank. "What's your name? And how do you happen to be with these fellows?"

"Why not?" said the other, answering the last question first. "I'm a rolling stone and joined up with this outfit because it looked like something doing. And that's what I want. As for my name, it's Roy Stone. And you guessed right. I am an American. Born an' raised in Wooster, out in Ohio."

He paused and looked curiously from one to the other of the boys. Tom Bodine was examining the two other prisoners for possible injuries needing attention. Stone nodded toward him.

"I can place a fellow like that, all right," he said. "Know this kind down here on the border. But who are you? You're only kids. What's your game? Are you with Obregon?"

"Is it safe to tell him who we are? He's an American. And, somehow, I have an idea he might help us."

"Well, it won't hurt, I guess," said Jack, doubtfully. "He might escape and betray us to rebel headquarters, but I suspect we can guard against that. Besides, he's bound to find out our identities, because those other two chaps will recognize you."

"Hardly in this rig," said Bob, referring to his clothing. "We talked all that over, you remember."

Bob and Jack had drawn aside during the whispered colloquy. Now Bob turned back to his prisoner.

"Look here," he said. "We'll have a little talk later. Right now we all need a good sleep."

Without more ado, Bob and Frank tied Stone's hands and led him to his bed, behind a curtain in one corner of the outer room. They considered that inasmuch as he was wounded, he was entitled to the bed. The German had recovered consciousness from the blow on the head dealt him by Tom, and the latter already had ranged him and the Mexican along the wall where the sentinel could keep an eye on them. For themselves, the boys pulled a heavy rug to another portion of the wall, spread the heavy hangings formerly covering the door to the inner cave on top, and here Bob and Frank lay down with their ponchos over them. Presently they were joined by Jack who had planned to mount guard the first two hours, but who had been overruled by Tom Bodine.

"No, you don't," said the latter. "I'm a tougher bird than you, and I take this job myself, an' that goes."

Too tired to protest very vehemently, Jack turned in after exacting a promise that Tom would call him at the end of two hours. The old cowman, however, had no such intention. It was not until eight hours later that he summoned Jack. The lights in the cave still burned brightly, for Tom had refrained from switching them off for the obvious reason that they made it easy to keep an eye on the prisoners. Day-light, however, showed at the mouth of the cave. When Jack noted the time, he began to scold.

"Forgit it," said Tom Bodine, gruffly. "You boys needed a good sleep while I'm an old hand at ridin' night herd. It didn't bother me none to stay up."

Without further words, he turned in and was asleep almost on the instant. Jack roused Bob and Frank, and while Bob mounted guard at the mouth of the cave where he could keep watch both on their prisoners and on the approach from below, the two others explored a rude pantry behind a curtain. They found a plentiful stock of provisions, which made it unnecessary for them to draw upon their own limited food supplies for breakfast.

When they themselves had eaten, they released the captives one at a time and fed them, afterwards replacing their bonds. The Mexican and the German were surly and uncommunicative. The latter tried to ply them with questions, but when they refused to answer he adopted a bullying tone and threatened them with all sorts of dire punishment. His threats, however, were no more effective at breaking down their silence than were his questions.

Bob remained at the doorway to avoid the risk of recognition by Morales and Von Arnheim as the youth who had foiled their attempt to steal Mr. Hampton's papers from his Long Island home. Jack, who had no means of knowing how much the traitor, Rollins, might have told Von Arnheim in the past about Mr. Hampton's personal affairs, watched keenly for some indication on the German's part that he had formed an idea as to their identity, but none was forthcoming.

"I suppose," he said to Frank, after Morales and Von Arnheim had been fed and returned to the other side of the cave, "that Rollins never bothered to speak about us because we were just boys. Then, too, you fellows arrived only the very day that we discovered Rollins's treachery and put a stop to his communications with these people."

"That may all be true," said Frank. "Probably it is. Just the same, Von Arnheim and Morales are bound to put two and two together and make a shrewd guess as to our identities, even if they say nothing to us about the matter.

"But," he added, confidently, "what if they do? We have them prisoners now and if we keep them well guarded until we have rescued your father, what does it matter how much they know?"

"We'll have to keep mighty strict watch, though," he said. "Well, now let's feed this American, Stone. I'll draw straws with you to see who keeps guard while Bob comes to get his breakfast at the same time. He wants to talk to Stone, he said."

CHAPTER XX

CONFERRING BY RADIO

Bob, however, told his companions he had decided not to interview Stone for the time being, and explained his reason, as well as what he hoped to gain from conversation with the prisoner.

"I believe," he declared, "that Stone is a warm-hearted, adventurous young fellow with no particular love for the Mexican rebels, but merely serving under their banner for the excitement. And I believe if we approach him right we can win his help in rescuing Mr. Hampton. He must know a good deal about this Calomares ranch and if we can get him to give us some pointers it will be worth while.

"That was what I had in mind last night. But mounting guard here this morning I had time to think it over, and I decided we had better go slow and, if possible, get the advice of my father on the matter."

"No, Frank, don't you see!" he said. "Bob is thinking of the radio here in the cave. Aren't you, Bob? I'm a simpleton not to have thought of it before."

"Well," said Bob, "we've all been so excited, that's not to be wondered at. But while I mounted guard here during your breakfast, I had a chance to calm down and do some thinking."

Bob was eager to use the radio telephone at once, but Jack persuaded him to eat breakfast first. The big fellow literally bolted his bacon, bread and coffee, and then accompanied by Jack, while Frank mounted guard, he retired to the inner room where the radio outfit was located.

"Let's have a look around here before we try to telephone," said Jack. "It will take us only a few minutes. And we ought to know what we have captured. What say?"

A cursory inspection quickly convinced Jack that the station was not of recent installation, but had been put in about the year 1918. Much of the equipment, while of the best at the time it was put in, had been antiquated since by improved parts.

It was a complete two-way installation, however, comprising a generator of practically sustained waves, a good control system to modulate the output, and a ground system for radiating a portion of the modulated energy as well as a receiver and a good amplifier.

"Here is this chimney in the rock about which Tom spoke," Jack pointed out. "They have hooked up through this. And the antenna, I suppose, is on top of the rock above us.

"This arc," he continued, advancing to the coils, "looks pretty strong and seems to have a rather elaborate water-cooling system. I think it is of foreign design, probably German. The Germans were early in the field with radio telephony development, you know."

"All right," said Bob, who was beginning to grow impatient, "I'll take your word for it. But what I want to know is, can we telephone my father at your ranch?"

"Say, Bob, I'm sorry," Jack said quickly. "You know how crazy Dad and I are over this radio telephone. But, of course, you are anxious to get your father. Come on, let's try. I'll throw on the generator."

Suiting action to words, Jack shortly had the generator at work, while Bob began calling through the air for his father.

"Be careful to use our code," Jack warned him. "You know Rollins said these fellows had a powerful radio station at the Calomares ranch, and if they were to pick up your call and listen in there'd be trouble."

"Right," said Bob. "But if Dave answers the signal, I'll have to ask for father, because Dave doesn't understand the code."

It was Dave Morningstar who answered, the other ex-cowboy employed as mechanic and guard at Mr. Hampton's radio plant in New Mexico. And when he had tuned to the proper pitch to hear distinctly and Bob's voice greeted him he was so surprised he stuttered and was incapable for a moment of coherent speech. Then he began to pour a flood of questions at Bob, wanting to know where he was, how he happened to be able to radio, what had happened to the boys, why Tom Bodine, his partner, had failed to return, and so on. But Bob cut him short.

"Stop it, Dave," he said. "We may be overheard. Call father to the telephone, so I can speak in code. Then I'll explain."

Fortunately, although it was past noon, Mr. Temple was at hand. So anxious was he about the boys that he had been unable to sleep during the night. All morning, despite the belief that it was folly to expect to hear from the lads so early, he had stayed at the radio plant. Now, when he heard his son's voice, there was heartfelt thanksgiving in his reply.

"Is it really you, Bob?" he asked, speaking in code. "I must have been insane to let you three lads go off on such a foolish venture. I have been tortured with anxiety every minute since you left. Tell me where you are and what has happened. And how in the world is it possible for you to radio? Are you all right?"

"Yes, we're all right, Dad," answered Bob, and there was a good deal of emotion in his voice, too. The big fellow and his father were real pals. "Don't you worry, Dad," he added. "We're doing well, thank you."

Then he retailed their adventures from the time of crossing the border into Old Mexico and leaving Tom Bodine at the boundary. There were many interruptions from his father.

"Thank heaven," said the latter, when learning that Tom Bodine had followed the boys and joined them. "He's a trustworthy chap, and to know that he is with you makes me breathe more easily."

When he came to relate the fight in the cave, Bob diplomatically made little of it. He felt there was nothing to be gained by unnecessarily harrowing the feelings of his father. The latter's anxiety, however, was great and he pumped rapid questions at his son which Bob could not avoid answering. The result was that Mr. Temple gained a fairly accurate idea of the peril in which the boys had been involved.

"But, Dad," Bob interrupted his parent's horrified exclamations, "it's all over now. None of us is injured, and we have got back our airplane."

"I know, Bob, I know," answered the older man. "But you can't understand a father's feelings. And it isn't all over yet by any means, for you haven't rescued Mr. Hampton. And you don't know what difficulties you will encounter in doing so, and what dangers you will run."

"Oh, I believe the worst is over, Dad," answered Bob. "We have captured Morales and Von Arnheim, and they were our two worst dangers. If we had encountered them at rebel headquarters and they had recognized me, our goose would have been cooked. We would have been taken prisoners, too. But now there will be nobody to recognize us. The rebels will take us for what we pretend to be, young Americans seeking adventure and riding in to enlist."

"Perhaps, Bob," said his father, only half convinced. "But let me think this over. There ought to be some other way to rescue Mr. Hampton now that you have the airplane again. Also you have these prisoners. It may be that you can gain some valuable information from them. Have you questioned them yet?"

Thereupon he proceeded to tell his father of Roy Stone, the young American in charge of the radio plant in the cave, whom they had made prisoner. A lengthy conversation ensued. Mr. Temple was reluctant at first to have the boys reveal their identities inasmuch as so far they had escaped detection. But he saw that if an ally could be made of Stone it would be of the highest importance to the boys. He finally authorized Bob to promise Stone a suitable reward, if he thought that would appeal to him. Then, enjoining Bob to take no further steps without first consulting him by radio, Mr. Temple concluded the conversation.

To Jack and Frank, speaking in low tones at the entrance to the cave where Frank kept guard, Bob explained the gist of his conversation with his father. Tom Bodine still slumbered heavily. Stone lay napping on his bed. Morales and Von Arnheim sat with drooping heads in the heavy chairs where, while Bob telephoned, Jack had thought it best to bind them.

"Well, let's talk with Stone and see what he has to say," Jack said. "Frank and I have been talking the situation over, too, and we've got all sorts of ideas. For one thing, we thought there was a chance the rebels could be persuaded to exchange father for Von Arnheim and Morales. Stone might know how important those two worthies are considered by the rebels."

"Can't I listen in on this confab?" Frank asked, plaintively. "Or must I continue to mount guard here? Besides, I want to go down and look at our airplane, and pat it even if I can't get in and fly. I can see it from here, and it looks tempting."

"You'll have to wait awhile to do that, I expect," said Jack with a smile. "We must decide what to do next before we spend any time playing."

At that moment, Tom Bodine yawned prodigiously and sat up on his make-shift couch.

"At least I can have a voice in the conference," said Frank. "If Tom's awake he can mount guard."

"All right, fine," said Jack. "We'll leave him out here with Morales and Von Arnheim, as soon as he has had something to eat. Then the three of us can take Stone into the other room and have a talk with him."

CHAPTER XXI

GAINING AN ALLY

Before mounting guard, however, Tom thought of their horses, a detail which the boys had forgotten in the quick march of events. He and Bob descended the slope, brought the animals into the valley where there was grass along the bed of a little stream trickling from a spring, and a few trees that provided shade. The horses were hobbled to prevent wandering too far, and then left to do as they pleased. They pleased, every one, to lie down at once and roll.

Upon their return to the cave, after Bob first had inspected the airplane and found it in tiptop condition and stocked with gas and oil, Tom mounted guard while the boys carried out their intention of taking Stone into the inner room for a conference.

Stone made matters easy for all concerned by speaking first, as soon as they all were out of earshot of Morales and Von Arnheim, and telling the boys he had guessed their identities.

"Of course, I don't know your names," he said, "but I reckon one of you is the son of that American bigbug old Calomares is holding prisoner up at his ranch. And the rest of you are his pals."

Bob's face fell. He had believed their identities were unsuspected. If this man could draw so clever a deduction, then their two other prisoners could do likewise. Moreover, if they carried out their original plan and went to rebel headquarters to enlist, would they not there, too, be suspected?

"Don't know," said Stone. "I haven't been given much chance to talk to 'em, have I? But that German is smart, and he may suspect. But"—and with this statement he set at rest a part of Bob's fears—"my bed is pretty close to this room an' I have pretty good ears. I overheard some things that Morales and Von Arnheim couldn't hear, especially when you used the radio to call your father. Anyhow, I thought it was your father. Mostly you spoke in code, but I heard you call him 'Dad' a couple of times."

"Until I made out who you were," he said, "I thought you were some wild-eyed kids looking for adventure an' comin' to the right place to find it. But once I got a suspicion, it was easy to figure out the rest. You see, I knew about your owning the airplane that Von Arnheim stole, an' about your radio stations. When you started the generator that showed me you knew something about radio, an' that was another clue.

"So I just put two an' two together. Anyhow, it finally came to me who you were. Am I right?"

"Yes," said Jack, taking the initiative as Stone concluded, "you are correct. It is my father who is held prisoner by the Mexicans, and these are my chums."

"We're in trouble," he said, simply, "and we need help that you could give us. How closely are you tied up with the rebels? You're an American and we are Americans. Does that mean anything to you?"

"Yes, kid, it does," said Stone. Despite the fact that he was only seven or eight years older than the three chums, he had led a roving life that had given him a world of experience and an older viewpoint, and he persisted in regarding them as youngsters. "I'm strong for the good old U.S.A.," he continued.

"But don't get me wrong. These are fine people down here, and don't you believe they ain't. Their standards aren't American standards either in manners or politics. But, just the same, they're good folks, and don't you let anybody tell you different. I wouldn't turn against them for anything. So, although your fathers have lots of money"—here he looked fixedly at Bob, who felt uncomfortable remembering his father's authorization to offer Stone money to help them—"well, don't offer me any, that's all."

"Good for you," he said warmly. "I'm glad to hear you talk that way. But"—and here Jack paused impressively—"suppose the imprisonment of my father threatened the peace and prosperity of the 'good old U.S.A.' as you call it. What then?"

"Shall we tell him what Mr. Temple says is behind all this?" Jack asked his companions.

"Well," began Jack, "it's this way." Thereupon he proceeded to relate Mr. Temple's theory that the attacks on the independent oil operators, the capturing of Mr. Hampton and the attempt engineered by Rollins and Remedios to capture himself, were all part of a plan to embroil the United States government with President Obregon, as the responsible head of the country whence the outrages originated.

"And Mr. Temple says," concluded Jack, "that if the two countries did come to war, it would hurt us very much with all Latin-America."

"Sure would," agreed Stone thoughtfully. "I've knocked about among these Spanish-American republics for years, an' they all look on the little old U.S.A. as a dollar-chaser and a bully." He was silent for a moment, and when he resumed, he said: "Look here. What you've just told me makes a big difference. You haven't said yet what you are out to do. But I can make a pretty good guess. You're going to try to rescue your father without letting the American authorities know anything about it. Am I right?"

"Well, I'll help you," said Stone. "I know where he is and how to get him, an' I'll tell you all I know."

Jack and Bob contented themselves with grasping Stone's hand warmly. Realizing Stone still was bound, Bob pulled out a pocket knife and started to cut his bonds, but Stone made him desist.

"Keep this dark from Von Arnheim and Morales," he said. "And keep me tied up. They may suspect I'm throwing in with you, but I don't want 'em to know. I want to be able to make a getaway, because these parts won't be very pleasant for me hereafter."

"That's right," said Bob. "Well, even if you won't take money, you'll have to let my father or Mr. Hampton help you in some way, with a job or something."

With Stone's aid won, the boys now set about learning from him how matters stood at the Calomares ranch.

For hours they continued to talk, so absorbed that they did not realize the flight of time until Tom Bodine came to inform them the sun was near setting and to ask what they intended to do that night. By then, however, they had obtained from Stone all the information he could give them, which was considerable; Bob had had another talk by radio with his father, and a plan for further proceedings had been worked out.

Jack and Bob were to make the attempt at the rescue of Mr. Hampton alone. They were to fly to the Calomares ranch in the airplane with Bob at the wheel, as Jack was not so experienced a flyer. Bob, on the other hand, knew his machine thoroughly, and was familiar with its every trick, a knowledge much to be desired as airplanes even more than motor cars and ships develop temperament and have got to be "humored," so to speak.

Frank rebelled at the part assigned him. He was to stay behind at the cave with Tom Bodine and Roy Stone, guarding the prisoners, Morales and Von Arnheim. When they had rescued Mr. Hampton, Jack and Bob would take him in the airplane and start flying to the Hampton ranch.

By means of the radio in the airplane, which could send 150 to 200 miles, although it could receive messages from a much greater distance, the Hamptons and Bob would notify the party left behind in the cave. Then Frank, Tom Bodine and Stone would ride for the border on horseback. Morales and Von Arnheim would be left bound so as to prevent their giving an alarm or offering any interference with the programme. After the party had been given time to make its way well along toward the border, rebel headquarters was to be notified by radio from the Hampton ranch of the location of the prisoners. The latter would, therefore, suffer nothing but inconvenience.

"But what fun do I get out of this?" lamented Frank, enviously regarding Bob and Jack. "You fellows get all the fun and all the glory. I ride tamely back to the ranch."

"It is hard luck, Frank," said Bob. "But your shoulder is sore and aching from your fight last night, and I'm in better condition to operate the plane. Besides, you know we can't take you, as the plane will hold only three and when we get Mr. Hampton we'll have our full complement. Some one of us has to stay behind. You've had your share of the fun so far, anyhow, and your turn will come again."

"I don't see it," said Frank. "It looks to me as if when you rescue Mr. Hampton the fun will all be over. But that's the way with you big bullies. Always picking on the little fellow."

"Well, you see," said Bob mischievously, "I've got to keep you out of danger for Della's sake. Ouch! Wow! Letup. Can't you take a joke."

For, lame shoulder notwithstanding, Frank leaped and, bowling the big fellow out of his chair, got astride of his writhing body and began to pummel him.

CHAPTER XXII

FLYING TO THE RESCUE

It was Bob talking, and the command was addressed to Morales and Von Arnheim. Tom Bodine stood guard over them with leveled revolver.

"Ask us no questions an' we'll tell you no lies," said Tom, waving his weapon. "Jest do what you're tole."

Sullenly the two men obeyed. When their outer clothing had been removed, and they stood revealed in light-weight undergarments—a well set-up powerful pair of men, about the height of Jack and Bob although neither was so sturdy as the latter—Bob halted them.

Scooping up the discarded clothing of the two men, Bob and Jack retired to the radio room. Stripping quickly, Jack dressed in Morales' clothing and Bob in that of the German aviator. This arrangement was adopted because Jack could speak Spanish with considerable fluency and thus fitted into the role of the Mexican. Bob, on the other hand, was better adapted to pass as the German who, they had been informed by Roy Stone, spoke Spanish only awkwardly.

They burst into hearty laughter, in which they were joined by Frank and Roy Stone, who were present at the transformation.

"To fellows that know Morales and Von Arnheim only by sight," he said, "you will pass for them easily enough. Both of them are smooth-shaven, which is unusual, for Mexicans and Germans both favor mustaches. But that's all the better for you boys.

"One thing you want to remember," he said to Bob, "and that is to walk pretty stiffly like you had a bone in your leg an' swallowed a ramrod. That's the way Von Arnheim always steps out, An' both of you keep your hats pulled down."

"Now you boys have got the bearings I gave you. You can easy enough find the landing field, even in the darkness. It's a big meadow as flat as a table, with the ranch house and outbuildings in a clump at one end, an' the radio station with its big tower supporting the antenna at t'other. Both places will be all lighted up, for Calomares lives like one o' them old-time barons an' he's always got so many men around the place he needn't fear nobody, so why put out lights? He likes light. He's a bug on it, in fact."

From the foregoing it will be seen that the boys had changed materially their original plan of riding in as adventure-seeking American youths to enlist in the rebel forces, and wait their chance to effect the rescue of Mr. Hampton. As matters now stood. Bob and Jack were to land in the airplane, and while Bob stayed by it, Jack was to make his way to the room where his father was held prisoner, free him, and guide him back to the airplane, when they would fly for the border.

Of course, the plan would not be so easy of execution as it sounded. To find the ranch and make a safe landing would be a fairly easy task. The ranch was not more than fifty miles distant by air line, and in that sparsely habited country there would be no other similar group of lights to puzzle Bob. Once they had alighted, however, the difficulties would be encountered.

At first the boys had considered the advisability of waiting until a late hour to make their attempt. Rebel headquarters then would have retired for the night, and they would run less danger of encountering anybody on landing. In that event, however, they soon realized, ranch and radio station alike would be dark and Bob would have no beacons to guide him to a landing.

No, there was only one thing to do, and that was to arrive at an early hour. Moreover, there would be this advantage attached, namely, that sentries would be lax and that, with many persons coming and going in and about the ranch, the passage of a familiar figure, such as they would take Jack to be, would arouse no comment. Jack might be halted, of course, by some one desirous of conversation. But he could make some excuse to pass on. As a matter of fact he planned to wrap a handkerchief about his jaw and pretend to be suffering from toothache. This would serve the double purpose of partially hiding his features, and of excusing him from indulging in extended speech.

"All right," said Jack, finally, as he finished donning his disguise by clapping Morales' hat on his head. "Let's go."

"Ya, ya," said Bob, doing a goosestep. Once more they all had a good laugh. Then Bob and Jack walked into the outer room of the cave, followed by Frank and Roy Stone. Stone had thrown caution to the winds, and had decided not to try any longer to hide his defection from Morales and Von Arnheim.

"I'll soon be riding away from here with you, anyhow," he told Frank. "And they'll find out then, if they haven't already suspected. I'm going down to the airplane to see the kids off."

Frank had demanded this privilege of going down to the valley and seeing Bob and Jack get away, and the others had no thought of denying him. So all four, bearing the oil torches kept in the cave by Stone for the purpose of lighting the landing field at night, descended from the cave. Tom Bodine was left to guard the two prisoners.

These had again suffered the ignominy of having their hands tied, after they had undressed, and, wrapped in the rubber ponchos given them by Bob, they had flung themselves down on the pallet prepared the previous night by the boys.

Stationed in the outer entrance of the cave, Tom Bodine looked around at the two prone forms several times. But always they lay motionless under their ponchos, and there seemed no cause for suspicion regarding them. Poor fellows, thought Tom, who held no particular animosity against them, they had had a hard time of it lately. After landing from a flying trip, they had been set upon and beaten. Then, made prisoner, they had spent the intervening hours cramped in bonds and in doubt as to what their captors intended doing with them. Probably were tired out and asleep by now, thought Tom. He even tiptoed over to where they lay and found, as he had expected, that both had their eyes closed and were breathing heavily.

Returning to the entrance, Tom took a step or two forward so as the better to see past the big rock outside and thus get a clearer view of the airplane. The boys had reached it by now, the oil flares were planted to both sides, and it was illuminated, standing out in the tossing light like a great bird.

As the propeller began to whirl, Tom took another step or two forward. An airplane was a new puzzle to him, and he was so interested in watching it get under way that he forgot his trust, forgot he had prisoners to watch, forgot everything but the mystery of that piece of mechanism, that gigantic bird, running bumpily now over the ground and now beginning to lift into the air, and now——

Tom whirled about. The old instinct of the man who lives much in the open, telling him danger is close at hand, was stirring at the roots of his hair. But he was just a trifle too late. As he faced about, a form shot out of the cave and Tom, totally unprepared for attack, was bowled over.

As he fell he let out a great wordless cry, thinking to warn Frank and Roy Stone. Then the butt of a revolver descended on his head.

CHAPTER XXIII

THE TABLES TURNED

"What was that?" asked Frank, turning to Roy Stone, as the airplane bearing Jack and Bob on their romantic adventure dwindled in the darkening sky. "I thought I heard a shout."

Both turned to stare upward toward the distant cave. There was no sign of movement. Only the dim bulk of the rock obscuring the entrance could be distinguished. They looked at each other, a nameless fear stirring at their hearts. Then Frank shook himself and laughed.

"Pshaw," said he, "this lonesome place seems spooky. I know what it must have been. It must have been Tom shouting a farewell to the fellows."

"Reckon you're right," said Stone, brightening. "Sure, that must be it. Well, let's go back. We'll be starting in a couple of hours, if all goes well."

"All right," said Frank, reaching to pluck one of the oil flares out of the ground.

"Just playing a hunch," said Stone. "I have the feeling that all may not be well up at the cave."

Frank dropped his voice unconsciously, as if fearing eavesdroppers in that lonely spot.

"To tell you the truth," said he frankly. "I feel the same way. I say! I have an idea. Let's edge out of the light without hurry, not toward the cave, but out that way," pointing in the direction taken by the airplane. "We'll put our hands up to our eyes and pretend to be watching the sky for the airplane's flight. It would be natural for us to want to get beyond the light of these torches, if we were trying to follow the boys with our eyes."

Beyond the light cast by the torches they paused. Darkness had descended now, in truth. Not even the shadowy bulk of the big rock before the entrance to the cave could be distinguished.

"Maybe we're making ourselves nervous over nothing," said Stone. "I feel kind of foolish. After all, what could happen? That old cowman pal of yours looks pretty capable."

"He is, too," said Frank. "Just the same, I feel we ought to be cautious. If Tom's all right when we reach the cave, well and good. But if he isn't———"

"You're right, kid," said Stone. "I'm no more of a coward than the next fellow. But if Morales and Von Arnheim by any chance gained the upper hand and got their clutches on me, I'd hear the birdies sing."

"Look here," he said, "isn't there some way we can sneak up there to find out if matters are all right or not? Suppose Tom has been overcome. We wouldn't stand much chance approaching the cave by the regular entrance." He paused and again stared upward. "We've been gone a considerable time," he said nervously. "You'd think if he were all right, Tom would have called to find out what is delaying us."

"Tell you what," said Stone, "I've got a little private path to the top of the cave where the antenna is located. It isn't much more than a goat track. But we'll have to be goats. Never been up it in the dark, but I think I can make it. Are you game to follow me?"

"Well, there's a fissure through the rock down into the cave. That's where the Germans that put in the radio plant made their hook-up. We can listen there, and maybe hear something to guide us."

"Oh, I remember that," said Frank, and added excitedly: "Maybe I could crawl down into the cave."

"You might be able to, at that," said Stone. "You're pretty slight. But it would be a ticklish proposition without any rope from above. Well, if you're on, let's go."

Turning he struck off across the valley, approaching the hill some distance from the path leading to the cave. Frank followed closely at his heels. Soon they began mounting upward. The climb in the darkness became more and more difficult, made more so by the care they exercised to prevent dislodging stones. They feared the clatter of these descending to the bottom would betray them.

Once Stone, who was in the lead, slipped and slid backward, clutching frantically to stay his fall. Fortunately, Frank was well braced at the moment and was able to stop him. After a rest to regain their breath and calm their shaking nerves, they resumed the climb.

At length Frank's feet were on level ground and ahead he saw the outlines of two latticed towers of familiar construction, and between them overheard the strands of the antenna. The Germans, Stone earlier had explained, had built the towers in such fashion that the crest of the hill hid them from the plain on one side while they were so far back from the edge of the flat plateau crowning the hill as to be also hidden from view from the valley.

Whispering an injunction to Frank to follow close at his heels, Stone crawled on hands and knees to the fissure in the rocks down which led the wires of the hook-up. It was not a straight descent into the cave, and no light came from it. But the two knelt in the darkness and put their heads close to the black opening to listen.

A murmur of speech could be heard distinctly, coming up through the hole. Frank could not distinguish the words, but with his limited knowledge of Spanish he was able to decipher that language was being employed.

"What is it?" he whispered to Stone. "Can you hear? Are they speaking in Spanish?"

His voice was anxious. Frank obeyed the command. In a moment, Stone lifted his head and said hoarsely:

"It's Morales. He and the German must have overcome your friend in some way. And I think he's got the Calomares ranch on the phone and is giving warning that your friends are on the way."

"Then when Jack and Bob land, they'll be surprised and captured. Oh, can't we do something?" Excitedly he jumped to his feet. "Let's put the radio out of commission."

"No, no. Wait a minute. The damage is done already. These fellows already have given sufficient warning to put them on guard at the ranch, even though they can't have told the whole story."

They stood undecided, looking at each other, in the starlit darkness. With an exclamation, Frank seized Stone by the arm. In his excitement, he shook it.

"Jack and Bob both clamped the headpieces on when they left in the airplane," he said. "And Jack tuned the radio to the pitch of this station, in order to be able to call us after rescuing his father. Why, he must have heard Morales give his warning! Yes, sirree. Why this isn't so bad!"

In their relief, the two laughed a trifle hysterically. In a moment, however, Frank sobered again.

"I see what you mean," he said. "Your friend Jack could call the ranch, too, and interfere so much that Morales' message would be all twisted up."

"That's it," said Frank. "And when it comes to thinking quickly and acting at once, you can count on Jack. Just the same," he added, "he can't keep that up forever, and when he lands—"

"Which he'll have to do shortly," interrupted Stone, "because the ranch is only fifty miles from here."

"Why, then," continued Frank, "these fellows can get their warning to the ranch and the boys will be captured, or at least their plan to rescue Mr. Hampton will be spoiled. No, sir, we'll have to wreck the radio plant here to give them a chance. If Jack has been able so far to interfere with the warning, and we put this plant out of commission now, they may be able to carry out their rescue after all. Let's see. How will we go about it?"

Both had been so engrossed they had failed to notice a dark form which, after creeping noiselessly up the slope, had started edging across the little plateau. Now this form suddenly straightened up and leaped forward. Frank cried out in alarm and jumped sideways, just as a spurt of flame split the darkness. The bullet sped by, leaving him unharmed. Stone, who was closer and stood with back turned, whirled about. The charging form cannoned into him, and he went down.

CHAPTER XXIV

FRANK SAVES THE DAY

Frank's first thought was to go to the assistance of Roy Stone. The latter and his opponent—in the darkness Frank could not distinguish whether it was Morales or Von Arnheim—were locked with their arms about each other and rolling on the ground. His second thought was as to the whereabouts of the other man.

He glanced about in alarm. Dark though the plateau was, however, he could see there was no other in sight. Bending down to the fissure in the rock, he could still hear the voice of Morales, and although he could not distinguish the words, he received the impression that the Mexican was angered for some reason. To Frank this meant that Morales was having difficulty in radioing the Calomares ranch, and his heart leaped with exultation. Jack had interfered.

A wild thought leaped full grown into his mind. Stone had given Bob a stiff battle; he probably would do the same to Von Arnheim, even though his shoulder was sore. What was to prevent Frank from slipping down to the cave while the two were engaged, where he could release Tom Bodine, surprise Morales and recapture the cave and the radio plant?

The next moment a feeling of shame surged over him. If Von Arnheim gained the upper hand, he would kill Stone without compunction. Putting aside his first thought, Frank ran to where the two forms still lay tightly locked on the ground, neither able to gain an advantage.

He bent down, and the first thing his gaze encountered was an upflung hand grasping a revolver, and another hand gripped about the wrist of the first and preventing use of the weapon. He surmised it was Von Arnheim who held the weapon, and acted accordingly.

Grasping the German's hand, he pressed back the fingers so sharply a cry of pain was wrung from Von Arnheim's lip. The revolver dropped to the ground. Its owner, however, pluckily continued the fight. Frank danced about, the captured weapon clubbed in his hand, ready to deal a blow when possible. But so furious was the fight that he feared to strike, lest he hit his friend.

Precious minutes were flying by. He was in an agony. Morales had to be prevented from radioing the ranch, if Jack and Bob were to stand their chance.

Then suddenly Roy Stone gained the upper hand of his opponent. He legs were twined about Von Arnheim, he clutched the other to his chest, one arm was in the small of his back, the other was pressed across his throat, his chin was sunk deep into the German's shoulder. Von Arnheim had only one arm free, the other was pinioned to his side. With this free arm he plucked futilely at Roy's arm across his throat, unable to reach the guarded face. It was a grip Von Arnheim was powerless to break, and it was only a question of time until he would be throttled into submission.

With a leap of the heart, Frank realized this. And bending down with his lips to Stone's ear, he said:

"I've got his gun. If you can hold him now I'm going into the cave after Morales. He's still at the phone."

A grunt was Stone's only reply as he pressed his chin deeper into the other's shoulder. Von Arnheim's body was beginning to arch like a bow. If he did not surrender soon, his back would be broken.

Morales was seated at the telephone as Frank entered the cave, captured revolver in his hand. His own weapon hung forgotten at his side, so little used was he to the handling of small arms. Frank had tumbled, fallen, rolled down the slope, taking no precautions, fired only with anxiety to prevent Morales from radioing while there was yet time.

The Mexican also, in his anxiety to reach the ranch and give the warning, had cast caution aside.

Across the outer room dashed Frank, scarcely noting the trussed-up figure of Tom Bodine flung in one corner. No hangings obscured the brightly-lighted interior of the inner cave, for they had been torn down the night before to form a pallet.

Frank darted forward and brought the butt of the revolver crashing down on the Mexican's head. Without a sound, without a gurgle or a cry, Morales swayed in the chair, then slumped to one side and slid to the floor.

With nervous haste Frank pulled the headpiece from the other and clamped it on his head. At once a crackle of Spanish words filled his ears. He could make nothing of them. What little knowledge of Spanish he once had possessed was not at his command now.

"Jack, Bob," he cried, pulling the microphone toward him. "This is Frank. Do you hear me? Frank."

"Use the code," cried Frank. In this emergency his brain was working lightning-fast. And in their own private code he added:

"It's all right now. They captured Tom Bodine while we were down in the valley seeing you off. But we've recaptured the cave."

"You saved our lives," came back Jack's voice. "I heard your Mexican friend call the ranch while we were flying, and at once started to interfere. It's been a job and my throat's hoarse. But he never got his message through, I can tell you that. Whatever it was he had to tell, I never did find out. I just started interfering, singing, talking, shouting. The ranch never found out what he was trying to say, and neither did I. But, boy, you're just in time. We can see the lights now. What? What's that?"

But Frank was too busy to answer his question. Morales had recovered consciousness and was on his knees and struggling to his feet, when out of the tail of his eye Frank saw his peril. Snatching the instrument from his head, he flung himself sideways. The impact of his body hurled Morales again to the floor.

Frank had placed the captured revolver on the table, as he telephoned. He would have to fight with his bare hands. Well, he would not let the Mexican overcome him and regain possession of that radiophone unless he killed Frank first. With hands gripped about the other's throat and legs twined about his body, Frank fought as he never thought he could fight. Morales was a heavy man, heavier even than Von Arnheim who had overcome Frank in that tempestuous fight in the darkness the night before. But his senses were still somewhat numbed from the blow on the head dealt him earlier by Frank, and the boy was fighting with a strength born of desperate resolve.

Frank's grip on the Mexican's throat tightened. Morales was unable to pluck those cruel hands away. His face became purple. His eyes started from his head. Suddenly he went limp beneath Frank, and sank to the floor.

Frank stood up swaying. The excitement and the strain of the combat had had their effect on him. There are mighty few boys of his age and build who could have gone through what he did and still keep their feet. Dancing points of light swam before his vision. He brushed a hand across his eyes to clear them. He reeled and would have fallen, but his hand clutched the table and steadied him.

What was it he must do? There was something which had to be done. Oh, if his head only would clear. Call Jack! Yes, that was it. Had to tell the old boy to go ahead—radio plant still Frank's—enemy couldn't get any warning from that Mexican fellow—had to tell him, had to.

Clutching the table, swaying, but with lips tightly pressed together and teeth clenched, Frank made his way to the microphone. Holding the headpiece to his ear, he set his lips to the telephone instrument and called:

It was there a moment later that Roy Stone found him, fallen in a heap across the body of the Mexican. Both were unconscious.

Stone was shaky himself. His battle with Von Arnheim had been a severe one, and the wound in his shoulder had started bleeding again. But as his gaze took in the situation, he turned to Tom Bodine, whose bonds he had cut on his way through the outer cave, and said in a tone of warmest admiration:

CHAPTER XXV

DANGER AT HAND

Bob as well as Jack had heard Frank's explanation of the occurrences at the cave, for he also wore a headpiece as he piloted the airplane. And it was with warm admiration toward the absent chum who so heroically had thwarted Morales' attempt to betray their hazardous expedition that he circled now above the two groups of lights which marked the Calomares ranch and radio station.

Smaller and smaller grew the circles, as with engine shut off he volplaned. The field was hard-packed and smooth and the plane alighted finally with practically no jar. When it came to a dead stop at last, Bob drew a long breath of relief. He had not been up for several weeks. And night flying above strange country to a landing on unfamiliar ground had been a strain upon him.

There were no mechanics running out to greet the alighting plane and trundle it into its hangar. Had this been a well-appointed landing field, such absence would have been suspicious. But to Bob and Jack it meant only confirmation of Roy Stone's remark that they were a "careless lot at the ranch."

The two chums stared around them, trying to pierce the darkness. They were in the middle of a long and wide field. A ring of low hills encircled them, the tops clearly outlined against the velvety sky. Overhead twinkled stars, brighter, warmer and apparently closer than when viewed in their Long Island home.

The hills on either hand were close. So, too, was the rampart at their back, over which they had flown. Those ahead were more distant, for it was in that direction extended the valley. Behind them was the radio plant with its tracery of tower and antenna against the sky and the windows of the power house gleaming from the light within. Ahead was a long, irregular clump of buildings set among trees. Some were dark. But the main structure, which they knew from Stone's description was the ranch house, was brightly lighted.

Try as they would to pierce the darkness, the boys were unable to discern anything other than this. There was not a human figure in sight.

They gazed with especial interest toward the ranch house, because it was somewhere within those walls that Mr. Hampton was held prisoner. Soon, if all went well, Jack would be making his way within in search of his father. At the thought, his heart which heretofore had been calm enough, began to beat rapidly and for a moment he felt as if he were about to suffocate. His breath almost failed him. It was a not unnatural feeling, and soon passed, but Bob noting the labored breathing climbed from the airplane and put an arm over his chum's shoulder.

"Righto," the big fellow answered. "I'm scared stiff myself, and I'm not even going into the ranch. If I were in your boots I'd probably be shaking myself loose from them."

The pleasantry was what Jack needed. He grinned at the thought of big Bob shaking so much with fear as to shake off his shoes, and his recovery was complete.

The plan was for Jack, in the dress and character of Morales, to go to the ranch house, enter boldly and make his way to the room where his father was held prisoner. Bob was to stay with the plane. Releasing his father, Jack would return with him. Then they would all three fly away across the international boundary to the north.

It was impossible to foretell, of course, what obstacles to the carrying out of this daring proposal would arise. Both boys felt certain, however, that so far they were not suspected, and that first Jack and then Frank had successfully thwarted the attempt of Morales to send a warning to the ranch by radio.

Neither was aware, of course, that the jumble of sounds through the air, when Jack from the airplane had interfered with Morales' attempt to warn the ranch, and later the code conversation between Jack and Frank, after the latter had obtained possession of the radio plant in the cave and had overcome Morales, had aroused the curiosity and then the suspicions of the young German, Muller, who operated the radio plant at the Calomares ranch.

A few moments before the beat of its engine in the sky signalized the approach of the airplane, Muller had decided to go to the ranch and report to Calomares. He had crossed the landing field afoot and had just reached the belt of trees when the machine volplaned to the field behind him.

Although, as has been said, his suspicions were aroused, Muller was far from suspecting the truth. He had no idea the airplane had been recovered by its rightful owners and that these latter were about to make a daring attempt to rescue Mr. Hampton. His thought on the contrary, was that something—he could not make a more definite surmise—had gone wrong at the cave.

Therefore, when, after standing several minutes at the belt of trees, gazing back toward the airplane, he saw a figure start from it for the ranch house, he believed it was either Von Arnheim or Morales coming to report.

Muller was a sycophant, the type of man eager to curry favor with those in authority. He decided he would gain the ear of the great Calomares first. That would detract somewhat from the glory of the other when he arrived. Turning he darted for the ranch.

Meantime, Jack was making his way ahead more slowly. While not attempting to hide, he was on unfamiliar ground and felt that it behooved him to follow implicitly the directions given by Roy Stone and make no mistakes.

Passing through the grove, Jack came in sight of the ranch. He paused in astonishment. Roy Stone's description of the great house had prepared him in a measure. Yet he was astounded. Here, indeed, was a palace in the wilderness.

The mansion stood on a slight elevation with a lawn in front sloping down to the trees from which Jack had emerged. In design it was like a country house of the ancient Roman aristocracy. The walls were of vari-colored brick with inlaid designs representing formal flowers. Two stories in height, with towers at the corners rising another two stories higher, the building was in two wings or sections, joined in front by a marble-tiled walk, roofed and pillared, but with the sides open. Inside, between these two wings, Roy Stone had told Jack, was an open court.

Nerving himself to the ordeal, and pulling down his hat to obscure his features, Jack crossed the lawn and started mounting the wide flight of stone steps flanked by crouching stone lions. He reached the marble tiles of the walk above and then, despite his anxiety to gain the left wing and the tower where his father was confined, he involuntarily paused.

The scene before him was one of the strangest to be found on the North American continent—this marble courtyard, with its overhanging balcony around the sides and rear and its splashing fountain and pool in the center, the whole illuminated by the soft glow of electric lights cunningly concealed along the edges of the balcony like footlights on the lip of a stage.

But it was not this alone which held Jack's gaze riveted and caused a smothered cry of surprise to burst from his lips. Involuntarily he stepped from the shelter of a pillar behind which he had been standing.

For approaching along the balcony of the left wing, Jack saw the loved figure of his father engrossed in conversation with a small, dark man of patrician bearing.

It was instinct rather than conscious thought which checked the cry on his lips. Instinct told him a shout would mean betrayal, and the shattering of his desperate plan.

Yet careless of who might see, he stood there looking up at the distant figure until it was lost to view, cut off by the outjutting roof above him. That one sight, however, lifted a vast load from the boy's mind. His father, at least, was not mistreated. Evidently the man with him was the Don. And as evidently his father was treated more as guest than prisoner.

At sound of a footstep on the marble tiles behind him, Jack returned with a start to a realization of his surroundings and the perils of his position. Assuming a carelessness which he was far from feeling, he refrained from turning about but instead started walking for that left wing ahead in the tower of which he knew his father to be lodged.

But the step behind him was accelerated, and he was hailed by name as Morales. Jack halted. Here was the first ordeal to be passed. Well, he was prepared for it. According to his plan, he had bound his face in a handkerchief and intended to pretend having the toothache. The swathings partly hid his features, and the pulled-down hat further obscured them.

CHAPTER XXVI

THE NIGHT ATTACK

When Jack's figure had become merged in the shadows of the grove, big Bob, standing beside the airplane, reached a decision.

"Not a soul in sight here," he muttered to himself, once more letting his gaze rove over his surroundings. "Jack thought it would be best for me to stay here, but nobody's going to monkey with the plane. I'm going to follow him—till he reaches the house, anyhow. He may need my help."

Thus the big fellow salved his conscience for departing from orders. But he was so eager to take a hand in proceedings that he felt it would be torture to stay behind. He was dressed in Von Arnheim's clothes. And his build was that of the German aviator. If he were observed, he would not be suspected. Even his atrocious Spanish would not betray him, as the German spoke the language almost as horribly as he.

When he reached the other side of the grove, and came in sight of the ranch house Bob, as Jack had done, halted in amazement at sight of the splendid structure.

He gazed around him. Nobody in sight. Shrubbery intervening prevented him from gaining a clear view of the house. He started to skirt the bushes.

Meantime, not far away, the conversation between Jack and Muller was nearing a climax. Approaching the pretended Morales, Muller asked what he had tried to convey in his radio call, explaining it had been so interfered with by another mysterious call as to be non-understandable. Not knowing Muller was the radio man at the ranch, Jack was nonplussed. Again he answered that he could not be delayed, and started to withdraw. Then Muller laid a detaining hand on his arm.

"Keep it to yourself, if you want to," Muller said. "But I know something happened at the cave and I have already reported so to the Don. First I thought you were trying to radio from the cave. Now here you come by airplane. There's—"

Muller still had no suspicion that the man before him was other than he pretended to be. Merely he was trying to pry into a matter that had aroused his curiosity. Jack, however, thought he was on the eve of being discovered, and was alarmed.

At this moment Bob, skirting a clump of bushes on the lawn below, came in sight of the two figures and halted.

He saw Jack wrench his arm from the other's grasp and turn to stride away. He saw the other raise an arm as if to stay Jack. And he saw the movement flip Jack's low-pulled hat from his head. It was accidental, but to Jack and Bob—the actor and the observer in this little drama—it seemed to be by intent. It is possible Jack still might have saved the day, had he stooped quickly, recovered his hat and clapped it on again before Muller could have seen his features.

As it was, however, Jack thought he was discovered. And he turned to deal with Muller. Then, in truth, he was discovered. Muller cried out in amazement. Then Jack landed a stinging blow on the mouth which sent the young German toppling to the marble pave.

At Muller's shout, several rebel sentries, who had been snoozing in the shadows beside the palace, instead of mounting guard, were startled into instant wakefulness. They came trotting in bare feet, long rifles in hand, and ran up the wide flight of steps.

Bob started forward to help Jack. The latter, however, took one look at the sentries and then dashed into the left wing of the building.

The sentries for a moment did not pursue, believing the fleeing man was Morales. Instead, they bent above Muller and helped him to his feet. Bob halted, and backed into the bushes, keeping his eyes on the scene. No use rushing in to help Jack now. He would merely succeed in getting into trouble himself, without aiding his chum.

From his vantage point he was able to read aright what followed. Although he could not overhear what was being said and would not have understood the Spanish words, if he had overheard, nevertheless he gathered that Muller was explaining the fugitive was not Morales, but someone wearing his clothes.

Then he saw the sentries dart away in pursuit of Jack, while Muller whipped out a revolver and fired three shots into the air.

"That's an alarm," Bob said to himself. "I'd better back off before this place is alive with soldiers."

Turning, he ran through the trees. Big Bob was not the one to desert a friend, but he saw no chance to help Jack now. On the other hand, he told himself, if he retained his freedom, he would be able to help Jack later perhaps.

Suddenly he carromed into a man running toward the house. Both rebounded from the contact. Bob saw the other was a Mexican with a rifle. Quick as thought, he lashed out with his right fist and caught the soldier on the point of the jaw. Totally unprepared for this attack, the man went down as if shot.

Bob ran on at redoubled speed, burst through the screen of trees, and dashed across the landing field toward his airplane. He had no definite idea as to what course to pursue. He and Jack, of course, had counted upon the possibility of Jack's being discovered. In that case, when he heard the alarm, Bob—supposedly sticking by his airplane—was to have flown away.

There were shouts behind him. Evidently his soldier victim had recovered. Perhaps, even, Muller had suspected the truth, namely, that if Jack were not Morales the aviator who had brought him was not Von Arnheim. In that case, Muller would be on his trail and he would have no time to lose.

The shouts behind him were not repeated. Perhaps, after all, his identity was not yet suspected and he was not pursued. Jack might be keeping all hands busy at the ranch.

In great leaps, he approached the airplane and, as he drew near, another thought obtruded itself. If he were to take flight in it, how was he to get away? Who would crank the motor by twirling the propeller?

This latter difficulty was quickly solved. Two Mexicans stood at respectful attention as he approached. Bob was dismayed for a moment, but then, seeing their awkward salute, he chuckled inwardly. They mistook him for Von Arnheim and evidently that German officer was a martinet who exacted a measure of discipline from the slovenly rebel soldiers.

Cracking an order at them in his best garbled Spanish, Bob clambered into the pilot's seat. He was understood, and better, was obeyed. One man gingerly approached the propeller and started twirling it, while the other went to the side of the plane and helped push it forward.

The propeller began to whirl furiously as Bob worked the starting mechanism. The Mexicans leaped out of the way. The plane began to bump ahead.

Shouts of anger burst forth at the same moment, there was the crack of a rifle, and a bullet sang unpleasantly close to Bob's ears. Out of the tail of his eye he could see a number of dark figures running toward him from the grove.

But Bob did not wait to be interviewed. With a swoop, the airplane left the ground and started upward. His pursuers were so close at hand they could almost grasp the wheels, as they leaped upward. Yet not quite. Bullets whistled about him, and several pinged against the body of the machine with a sharp metallic ring. Bob thanked his stars that the plane had an all-metal body. Once above pursuit, he was safe from stray rifle shots.

With a curse the baffled Muller, who had been quick to realize that if one masquerader was not Morales, then the other was not Von Arnheim, watched the airplane shoot away at dizzying speed and disappear beyond the guarding hills to the north.

Then he turned back toward the ranch house, eager to learn how the pursuit of Jack had ended.

But for young Herr Muller and the Calomares ranch in general the night alarms were not ended. In fact, they had just begun.

Before Muller on his return trip had reached the belt of trees, while the search for Jack, who had mysteriously disappeared, went on merrily within the Calomares palace, and while Bob was yet flying over the hills to the north, rebel pickets below him were attacked by Mexican government troops.

The rebels on the northern rampart of hills defending the natural amphitheatre where the Calomares ranch was located, fell back hurriedly. They were outnumbered.

Out of the huddled buildings, which the boys had only glimpsed at the rear of the great ranch house boiled scores of rebel soldiery, rubbing the sleep from their eyes, hugging their rifles as they trotted forward in bare feet. Within the house, the search for Jack was temporarily abandoned, while the peppery little Don Fernandez Calomares, alarmed at this night attack which might mean that the government troops were in force, hastened to take command outdoors.

To Bob, who having crossed the crest of the hill had shut off his motor and volplaning, the shots and cries of the attackers came distinctly. He had intended making a hazardous landing beyond the rebel lines and returning afoot to try and rescue Jack. But this newest development in the situation caused him to open the motor and start to spiralling upward.

CHAPTER XXVII

SENORITA RAFAELA

After bowling Muller over and fleeing from the sentries drawn by the latter's shout, Jack ran through the great arched doorway into the left wing of the palace. Ahead lay a dark corridor, upon which opened the doors of the ground floor rooms. He was in a round entranceway from which ascended a flight of winding stone steps to the balconied upper floor and the turret rooms above. Up there, somewhere, was his father. Jack paused only a moment, then sprang up the steps.

As he reached the upper landing, he heard the sound of footsteps descending from the tower. He listened a moment. They were not the familiar footsteps of his father.

He must act quickly, if he were to stand any chance of escape. Springing forward, revolver in hand, he seized the knob of the nearest door on the balcony, found the door give and leaped in, pushing it to behind him and setting his back against it.

The room was brightly lighted, evidently a young lady's boudoir. This much his first glance showed Jack. It showed him also two women—one young and very beautiful, the other wizened and monkey-like, both terrified and speechless. They were Don Fernandez' daughter, Rafaela, and her duenna or chaperone, Donna Ana.

He listened with strained attention to sounds from outside. The menacing footsteps reached the landing, and then continued to descend. Jack turned the key in the lock. He was none too soon. A moment later the padding of the bare feet of the sentries sounded muffled outside, then grew fainter as the men separated, one ascending the stairway of the tower, the other running along the balcony.

Jack was puzzled as to what next to do. From Roy Stone's brief description of the Don's family, he guessed at the identities of the two women. While he stood irresolute, the girl recovered from her fright. Her dark eyes flashed, and she commanded him in an imperious tone to lower his weapon.

"Very well," said the girl. "But who are you? You cannot escape. My father will capture you."

In the rapid march of events, the handkerchief with which he had bound up his jaw had become loosened. Now it fell, revealing Jack's handsome features and his close-clinging mop of dark curls.

"Why, you are just a boy," declared Rafaela, and her eyes lost some of their hostility while at the same time, unconsciously, her voice became less harsh.

"Surely," she said, turning to Donna Ana, "this lad can have done nothing so terrible."

The prim, black-robed duenna had gained courage from her mistress's temerity. She had ceased trembling. Yet she was exercised about something. Jack could not understand why. Surely, she was no longer fearful of him. She leaned closer to her young mistress, seated at a low writing table, and whispered in her ear. Rafaela threw back her head and laughed—a low, musical laugh that sounded fascinatingly pleasant in Jack's ears, worried though he was.

"My dear Donna Ana," said the girl. "What if he is a man! And in my room! Are you not here to watch over me? And I do not believe he will bite. No, no. See, he is such a nice young man that I can chuck him under the chin. So!"

And suiting action to words, the girl sprang from her chair, walked swiftly across the room and chucked Jack under the chin.

To say that Jack was surprised would be a mild statement. From his knowledge of Latin-American girls gathered in Peru, he believed those of good family invariably were convent-bred and extremely decorous in the presence of young men. He was so dazed at the girl's action that her next move, which was a lightning-quick attempt to grasp his revolver and wrest it from him, almost succeeded.

Jack retained a grip on the weapon, however, and managed to prevent Rafaela from obtaining it. Foiled in her attempt, all her bravado deserted her and running back to her chair, she sank into it and began to weep.

What in the world should a fellow do in a case like this? Jack didn't know. Usually, he was equal to emergencies, but this one was something beyond his understanding. He stood helpless, while the duenna alternately glared at him and patted her young charge on the back, muttering soft words of comfort to her meanwhile.

Quickly as the shower came, however, it disappeared. Rafaela pushed Donna Ana aside impatiently and looked at Jack, smiling through her tears.

"Well, sir," she said, demurely, "that did not succeed. What do you intend to do with your prisoners?"

"Look here," he said, sensing a kindred spirit. "I'm not a rascal. You will have to believe me. I haven't done anything so terrible, after all. You need not be scared of me."

"But who are you, then?" asked the girl. "Listen. They are shouting through the house. Soon they will be making a search from room to room."

Jack started. If that were true, when the searchers came to this locked door, what would happen? He thought for a moment. The daring idea to take the girl into his confidence and enlist her aid had been budding in his mind. He regarded her keenly for the first time. Would she help? Perhaps the romantic nature of his enterprise would appeal to her, even though he was fighting against her father. Well, it would do no harm to try.

And speaking rapidly in his fluent Spanish, in a few brief statements, he laid before her the main fact that Mr. Hampton, whom she doubtless knew, was his father, and that he had come to the rescue in an airplane.

"Only now," he concluded mournfully, "I have been discovered. I expect my chum will be forced to fly away. And it looks as if I were bound to fail."

During his recital, the girl's eyes had grown bright with interest. She leaned forward, listening with eager attention. As Jack ceased, apparently she was about to speak, but there came a tattoo of knuckles on the door which caused her to halt abruptly.

"Our deliverers," murmured Donna Ana, who had never entirely ceased trembling, and she cast a spiteful glance at Jack. To the duenna, young men, and especially one so unceremonious, were terrible creatures.

"Silence," hissed the girl, and the old duenna in evident fear of her imperious young mistress, trembled the more.

Rising, she seized him by an arm and partly led, partly pushed him to the chair upon which she had been sitting. It was a wicker chair, with wicker-latticed sides extending clear to the floor. Lifting it, she ordered Jack to kneel down and crouch into as small a space as possible. He complied. Then she clapped the chair over him. He was completely hidden, except in front, where the wicker latticing did not extend.

Seating herself calmly in the chair, Rafaela so disposed her skirts that Jack could not be seen. Then she picked up her pen and sat as if just interrupted at her writing.

The knocking on the door was repeated, louder this time, and the voice of the Don himself impatiently bade that the door be opened.

And she shot at Donna Ana a terrible glance, which caused the latter to cringe. Evidently, the duenna stood in considerable awe of her temperamental young mistress.

The old woman unlocked the door and stepped back, revealing on the threshold Don Fernandez with several armed retainers at his back.

"What does this mean?" he demanded, glaring at his daughter as he advanced a step or two into the room. "Locked doors at so early an hour?"

"Why, papa, dear, we heard the shouts and several revolver shots," said his daughter. "Was it not natural for two lone women to lock their door?"

"Papa, what is the matter? What is the meaning of all this noise? Of those shots?" Rafaela anxiously inquired.

"Some man impersonating one of my lieutenants gained entrance," said the Don. "I believe him a government agent. He may have come to attempt my life."

Frantic lest she might betray herself and him, Jack reached forward cautiously and tapped the tiny ankle dangling before him.

He was none too soon. Thus brought to a realization of her position, Rafaela checked the words.

"Why, papa," she answered, "I was going to say he couldn't be so mean. To come here to kill you. Oh, no. That would be too terrible."

"But I do believe it," affirmed the Don. "What do you know of how politics is carried on in our poor, distracted country? Tut, tut, you are just a girl. What I came to ask was whether the man had hidden here? We have searched all the rooms on this balcony, without success. Yet most certainly Pedro and Pancho"—indicating the armed men in the corridor—"saw him bound up the stairs."

Before Don Fernandez could retort, the report of distant rifle fire came to the ears of all in the room, followed by a growing fusillade as the sentries on the northern rim of the valley fell back before attack.

"Hark," said he, and added with conviction: "The government troops are attacking. And they sent an assassin ahead of them. Well, he has been foiled. And they will be foiled, too."

And without more ado he darted from the room, Pancho and Pedro obediently following at his heels.

CHAPTER XXVIII

THE FAIR TRAITRESS

Rafaela leaped up and lifted her chair, permitting Jack to emerge from his unique hiding place. He was overcome with gratitude at the thought of what she had done for him, and hesitated to speak.

"Oh, I want to believe you," cried the girl, twisting her hands. "But father was so positive."

"Nonsense," she declared, sharply, glaring at her duenna. "Cannot you see this young man is telling the truth? I," she declared proudly, "can tell a truthful person from a liar at once. And I declare to you this young man is truthful."

Jack smothered a smile. The girl was as changeable as a weathercock. And calling him "young man" in that lofty tone, too. Why, she was little more than a youngster herself—couldn't be as old as he.

"Come now," said the girl suddenly, seizing him by the hand. "We have no time to lose. Now is your opportunity."

"Yes, yes"—impatiently. "While the government troops attack, you must release your father and escape."

"Have I not said so?" asked Rafaela impatiently. "And it seems to me I have already been of some trifling aid—actually?"

The sarcasm was not lost on Jack. But he ignored it. Finding he still held the hand she had extended when urging him to follow her, he squeezed it.

"You are not a very accomplished courtier, Mr. Jack Hampton," she said, withdrawing her hand.

Jack would have protested. He was rapidly falling under the spell of her charm. But she halted him with an imperious gesture.

"We are wasting precious time," she said. "Come." Then, turning to Donna Ana, she said sharply: "You will stay here until I return. And if you betray me—" Again she made a threatening gesture, and again the old duenna cowered. Thereupon, the girl hastened from the room and Jack followed.

Up the spiral stone stairway of the tower ran Rafaela, passing the first landing where burned an electric light. Jack was close at her heels. At length they reached the top landing, and stood before the single door there. It was of stout oak, heavy and ponderous.

So near to a successful conclusion of his adventure, Jack's heart beat so rapidly that once again he experienced that sensation of suffocation which had seized him on landing from the airplane.

In the dim light on the landing, they stared at each other in dismay. Here was a contingency which had occurred to neither.

The whispering, the careful trying of the door, the sound of their footsteps—these had aroused Mr. Hampton from his reading on the other side of the door.

"Dad," he whispered tensely. "It's Jack. Don't make a noise. I've come to rescue you."

There was a moment of silence, then the sound of rapid footsteps crossing the room.

"Jack?" Mr. Hampton also had stooped to the keyhole. "It can't be. Yet that voice! My boy, my boy. But how in the world did you come here?"

"Then," said Jack, despairingly, "it looks as if we were balked at the end. This door is too stout to break down without bringing the enemy on us. It's thick and bound with iron straps besides."

"Dad, we'll have to break down the door. The government troops are attacking. Even if we do make a lot of noise, it may go unnoticed. Have you a heavy chair you can use?"

"Yes," answered his father. "But, wait. Government troops attacking, hey? Then that is the meaning of those shots which caused Don Fernandez to leave me so hurriedly."

"No, Dad, those first shots were when they sounded the alarm on discovering me."

"They discovered you?" Mr. Hampton groaned in mock dismay. "Oh, this is too much. But, Jack, what I started to say was that as Don Fernandez dashed down the steps, I heard him drop something in his haste that rang on the stones. Maybe that was the key."

Jack stood upright, and communicated to the impatient Rafaela what his father had said. She had been unable to hear. Fortunately, he carried an electric torch. Swinging this so that the light fell on the steps, he started downward. Before he had gone three steps, the girl's quick eyes saw the key gleam in the light. She snatched it up with an exclamation, turned, inserted it in the keyhole, and the door swung in.

Jack leaped through the opening, and the tall and handsome man, to whom he bore so striking a resemblance, enfolded him in his arms.

They drew apart and stood looking at each other. There was more than a suspicion of moisture in each pair of eyes.

Mr. Hampton's gaze fell on Rafaela, with whom he had had a number of pleasant conversations during his captivity. He dropped a hand on her shoulder.

"My dear girl," he said. "You never did a kinder deed. I hope you will not have cause to regret it."

"Oh," said she with an arch smile. "Papa would be furious if he discovered what I have done. But I can manage him."

"But you must not delay," added Rafaela, anxiously. "Even now the firing seems to be farther away. My father keeps many soldiers here. And he is, doubtless, driving away the attacking party. You must go quickly before he returns, and while all is confusion."

"I arrived by airplane," said Jack. "But whether we can get away by the same means is another matter."

"The younger generation moves too fast for me," he said. "But will you please explain?"

"It's a long story, Dad," said Jack, "and I haven't the time. But it's Bob's airplane. The fellows who kidnapped you stole the machine in Long Island several days before that. Well, Mr. Temple and the boys came out to New Mexico, and we recovered the plane and, and—well, there you are."

"Yes, I see," said Mr. Hampton. "It's as clear as a New York fog. But it's enough to know that Bob—didn't you mention his name—is here with the machine. Let's go and find him."

He started for the door. But at that moment Rafaela, who stood closer to it, halted him with upraised hand.

"Quick, Jack," whispered Mr. Hampton, "you mustn't be seen. Nor you, Miss Calomares. Here, hide behind this bed. And he pushed the two behind the hangings of a great four-poster. Then removing the key from the outside of the door, he hurriedly but noiselessly swung the ponderous frame shut, and locked it on the inside.

"Calomares won't recall losing the key," he said grimly to himself. "There may be a chance yet."

He listened with his ear at the keyhole. The cautious footsteps mounted higher. They reached the landing. Then there was a low knock on the panel, and a voice called low and urgently:

CHAPTER XXIX

THREE CHEERS FOR THE RADIO BOYS

Mr. Hampton unlocked and opened the door, and greeted the big fellow as warmly as he had his own son.

Jack, who was peeping from behind the four-poster, sprang into the room, and slapped his chum resoundingly on the back.

"Hurray," he said. "So they didn't get you after all? When I saw you punch that fellow I thought your goose was cooked."

"Then when the attack began," he added, "I flew around overhead until I saw my chance to return and land. I wasn't going to leave without you. Presently, the government troops were beaten at the north. That was only a feint on their part, anyhow, I believe, to engage the attention of the rebels. For at once, heavy shooting broke out farther down the valley. Sounded like the main body was attacking there. Then the rebels scooted down that way to repulse the new attack, and I took a chance and landed. Not a soul in sight. And here I am."

"Bob, I'm proud of you," said Mr. Hampton. "Well, let's hurry away before it is too late."

Bob looked at her in astonishment. Mr. Hampton, with a twinkle in his eye, viewed Jack ardently. The latter advanced with extended hand.

"Miss Calomares," he said, "I can't tell you how grateful I am. I hope we shall meet again."

"Miss Calomares?" muttered Bob, under his breath, his eyes on the beautiful girl. "Jack certainly has moved fast. I don't get this."

"Miss Calomares," he said, leading Bob forward. "This is my son's chum. He came with him tonight in his airplane."

"Come," said Mr. Hampton, and once more moved toward the door. Once more, however, his steps were arrested by a noise outside. This time they heard the shouts of many men approaching the house and crying "Viva, Calomares."

"Too late," groaned Mr. Hampton. "They have driven off the attack, and are returning."

"Oh, I must go to my room before papa discovers me here," she cried. She darted for the door, but paused to give them parting cheer. "Do not give up hope," she said. "They will drink a great deal, and then all will sleep very soundly. You may escape late tonight. Good-bye," and turning, she ran lightly down the steps.

Jack's eyes followed. At the turning, she paused, looked back, and waved to him, then disappeared.

"You boys hide behind the bed," said Mr. Hampton. "I'll close the door, but I won't lock it this time, for on second thought I believe if it were locked and Calomares came up to see me—as he frequently does before retiring—it would make him suspicious. I shall leave it unlocked, and then he will believe he left it so himself in his haste."

"Well, Dad," said Jack, turning to his father, "didn't you say Don Fernandez comes to call on you before retiring?"

"Yes, we have become good companions. He guards me carefully, keeps me a prisoner for his own ends, but he is a cultured man and we have much in common."

"Father says," asserted Bob, "that you are being held prisoner in order to make trouble between the United States and the Mexican government."

"He is correct," approved Mr. Hampton. "Don Fernandez has not attempted to conceal from me that that is his desire. He sent a demand for a preposterous ransom, merely in order to precipitate action at Washington, and he has been wondering why no action was taken."

"Well, that's what father thought," declared Bob. "So he has kept the matter of your being kidnapped a secret. Instead of appealing to our government, we set out to rescue you. Father says we must do our utmost to avert trouble between Mexico and the United States."

"So that accounts for many things," said Mr. Hampton. "I'm glad to have them cleared up. But we are forgetting your idea, Jack. What is it?"

"Simply that we capture Don Fernandez and make him release us all under a guarantee of safe conduct," said Jack.

"I believe it can be done," said Mr. Hampton. "And here," he added, listening, "comes our opportunity, if I am not mistaken. You boys get behind the four-poster and wait until I give you your cue."

Noiselessly Mr. Hampton closed the door, as the boys went into hiding. Then the older man resumed his seat by the table, picked up his book, and appeared to be reading.

Quick, light footsteps sounded on the landing outside. There was a pause, while Don Fernandez searched his pockets for the key to the door. Unable to find it, he turned as if to depart. To three pairs of ears, straining to hear his every movement, the interpretation was clear. He believed he had locked the door and lost the key and was about to depart. Mr. Hampton saved the situation by raising his voice, and calling:

"Is that you, Don Fernandez? Will you not honor me by coming in? I am eager to learn what has occurred."

The Don decided to try the door. To his surprise, it opened to his touch. "I must have forgotten to lock it in my haste," he muttered, and stepped into the room.

"Government troops," he said, advancing, "They thought to surprise us but we have beaten them off decisively." He sat down heavily. "It has been strenuous work," he said. "But that is over. Now to find the assassin, if he has not already escaped."

"Assassin?" queried Mr. Hampton, in genuine surprise. He had not been told the Don's belief regarding Jack.

"Yes," said Don Fernandez, violently. "That miserable Obregon." And he proceeded to relate his version of Jack's arrival.

"Oh, but you are mistaken," said Mr. Hampton, coolly. "That was no assassin, but my son. He came to attempt to rescue me."

"Your son?" he cried. "Came to rescue you? Preposterous. Then, why are you here?"

"Because," said Jack, stepping from hiding, with revolver leveled, "I wanted to meet you."

"Yes, and so did I," said Bob, not to be outdone, as he emerged, also with leveled weapon, from the other side of the four-poster.

Mr. Hampton quickly slipped the key into the lock of the door, turned it and drew back. Don Fernandez saw the action. He glared from one to the other of the three, and then sat down with a resigned shrug of the shoulders.

"You wanted to meet me?" he said. "I am honored. But, Mr. Hampton, there is not only one son but two!"

"Not exactly," said the American. "This lad"—laying a hand on Jack's shoulder—"is my son, the young man you pursued for a time tonight. This other"—placing his other hand on Bob's shoulder—"is my son's chum."

"Well," said Don Fernandez, the faintest suggestion of a twinkle in his eye, "now that you have met me, as you desired, what have you to say?"

"Just this," said Jack, boldly, "we want you to permit us to leave under safe conduct. We want to take father with us in Bob's airplane. Oh, yes, it was my chum's airplane which your men stole in Long Island. But we have gotten it back again."

"So?" said Don Fernandez. "Well, nothing surprises me tonight. And where, may I ask, are Morales and Von Arnheim? I see you are wearing their clothes."

"We have got them imprisoned," said Jack. "But we are in earnest, sir, about this. We are armed and have the upper hand, and we mean to have your protection. If you are armed, you had better give your weapon to father."

"As your father very well knows," said the Don, "I never carry weapons. And now"—with grave courtesy—"if you will permit me, young sir, I would like to speak privately with your father."

At a nod of agreement from his father, Jack withdrew to the door, followed by Bob, leaving the two older men in low-voiced conversation. They spoke animatedly, and to the anxious boys there came more than once a low chuckle of laughter from Don Fernandez while they could see Mr. Hampton beginning to smile. At length, Don Fernandez beckoned imperiously, and the boys approached.

He regarded them with twinkling eyes, but it was Mr. Hampton who acted as spokesman.

"Boys," said he, "Don Fernandez consents. But I do not believe he was influenced by fear for his life."

Don Fernandez stood up between the two chums, and put an arm over the shoulder of each—or, rather, tried to, as they towered above him.

"No, it was not fear," said he. "But Mr. Hampton has told me a little of what you have done, and I see it is useless to fight against Young America. You are fine fellows. If I had a son"—wistfully—"I would want him to be like you."

CHAPTER XXX

GOOD NEWS FOR ANXIOUS EARS

He and Jack, escorted by several Mexicans of Don Fernandez' band who had been informed by the Don himself that the boys were friends who were to be treated with every respect, were approaching the radio station of the Calomares ranch.

Jack was exuberant. Plans for the rescue of his father from the stronghold of the rebel leader had not worked out just as proposed. Yet the wild adventure upon which he and Bob had embarked had come to a successful conclusion, after all. And he was correspondingly elated.

Jack and his father were close pals. And he knew that Bob and his father were the same. He threw an arm over the shoulder of his chum.

"Your father will certainly be relieved," he said. "I imagine he has been sitting up there at the radio station on our ranch in New Mexico for hours, waiting to hear from you. I can just see him in there, walking up and down impatiently, with that bow-legged old cowboy, Dave Morningstar, tilted back in a chair, with his hat down over; his eyes, smoking and never making a move."

"And Frank, too," said Jack, thinking of the third chum, left behind at the cave.

"Good old Frank," said Bob, warmly. "We've got to tell him as soon as I've notified father."

"He certainly put up some fight, I'll bet," said Jack, thinking of the hurried radio reaching them from the cave as they neared the Calomares ranch in their airplane hours before. "And maybe he was hurt in that fight with Morales. He said he licked the Mexican, but that was all we heard. You remember? His voice was broken off after that."

"That's right," said Bob. "I hope nothing serious happened to him. What a shame it would be if he was hurt, while here we came through practically without a scratch."

All this time they had been walking across the starlit landing field, where could be seen Bob's airplane, and now they drew near the brightly-lighted radio station.

Entering the sending room they were confronted by Muller. That young German operator, whose perspicacity almost had caused their undoing and whom Jack earlier had floored with a blow on the chin, was sitting in a chair reading. He had returned to the station after the attack of the Mexican regulars had been beaten off.

Muller jumped to his feet, surprise giving way to anger, but before he could draw and level the revolver swinging at his hip, one of the Mexican guards accompanying the boys pushed them aside and thrust himself forward.

"None of that," he said in Spanish. "The General has commanded that these young Americanos be well treated. They are friends."

"Friends," muttered Muller, sullenly, nevertheless withdrawing his hand from the revolver butt. "That wasn't a very friendly way to treat me awhile ago."

"And why, if you are friends," he demanded, "do you two appear in the clothing of Herr von Arnheim and Captain Morales?"

"A number of events have occurred," said Jack, quietly. "That is why. However, Don Fernandez has heard the tale, and that is sufficient. He has given orders personally to these soldiers that we shall be permitted to use the radio. That is why we are here."

Grudgingly, Muller stepped aside. Here was a mystery, and he hated mysteries. Besides, these two youths were Americans. He was a German and although the war between their respective countries was at an end, he could not bring himself to entertain kindly feelings toward them. Like many Germans, he believed the United States responsible for the defeat of his fatherland in the World War. He was working in the ranks of Germans in Mexico to embroil the United States with that country. Such war, he believed, would strike a blow at the prestige of the hated Yankees.

"Look here," said Jack, flushing at this grumpy attitude, but deciding to do the manly thing, nevertheless, and extending his hand, "let bygones be bygones."

After a moment's hesitation, Muller shook hands. To do him justice, it is only fair to point out that he was sincere in his attitude toward Americans, but misled.

"I haven't time to explain about that blow," said Jack, "but at the moment it was necessary. Matters have changed since then. It was nothing personal."

"Very well," said Muller, his grumpiness beginning to disappear beneath the charm of Jack's manner. "Say no more. Now what is it you want? Perhaps I can help you."

"We want to use the radio," said Jack, noting Bob's growing impatience at their delay.

"The Hampton ranch," interrupted Bob, who decided it was time to bring this conversation to an end. He was in a hurry to talk with his father.

This reminder of the erstwhile traitor at the Hampton ranch brought both boys to a realization that Muller was familiar with the manner of calling their station, as undoubtedly he had handled or conducted radio conversations with Rollins in the past.

"No, not Rollins," said Bob, shortly. It was all right for Jack to shake hands with Muller if he wanted to. Jack and Muller had been active opponents, and such an act was only sportsmanlike under the circumstances. But Bob disliked the young German on sight. "Just let me at the phone," he said, "and turn on the juice."

Muller turned stiffly and entered the power plant adjacent, while Bob in a fever adjusted the headpiece. As the hum of machinery sounded from the power plant, Jack laid a hand on Bob's arm.

Bob regarded him inquiringly, his fingers reaching for the knobs on the instrument box before him, preparatory to sending out his signal call.

"Well, you know old Frank will have his ear glued to the receiver at the cave. Suppose you call your father, but tell Frank to listen in and not interrupt."

CHAPTER XXXI

CALM AFTER THE STORM

Meanwhile, as Jack had foreseen, Mr. Temple waited at the radio plant at the Hampton ranch with ill-concealed impatience.

Dave Morningstar, hat pulled down over his eyes, sat in a chair tilted back against the wall, watching him from beneath the brim. The only signs of life about the ex-cowboy turned mechanic were the occasional movements of the eyes, and the occasional refilling of his pipe, from which lazy streamers of smoke now and again floated upward.

All the evening these two had held watch. And, as hour after hour passed, with no word from the boys, Mr. Temple's anxiety rose to a fever. He condemned himself for ever having given his consent to his son and Jack starting upon so foolhardy an expedition as that of attempting to rescue Jack's father from the rebel headquarters and fly to safety with him in Bob's airplane.

Surely, he thought, the boys long since would have reached the ranch and made their departure. They had promised to call him by radio from the airplane the moment they started on their return flight. From their failure to do so he argued the worst. Their expedition must have come to grief, probably even now they were prisoners, perhaps—

But he shuddered to think of the alternative. He would not let himself consider that possibility. In desperation he turned to Dave Morningstar.

The old ex-cowboy took his pipe from his mouth, spat deliberately to one side, then brought the forelegs of his chair to the floor.

"Le's see," he said. "I been a'most asleep. Le's see. What say to calling the cave?"

"Yes, certainly," he said. "Why haven't I thought of that before? Perhaps Frank has heard something."

He did not pause to consider that the party at the cave in all likelihood was little better prepared than he with information. The mere idea of doing something, of taking some action that would break up this horrible spell of waiting, appealed to him in his excited state.

But after hearing from Frank an account not only of the fight the latter had had to recover the cave, after once having been dispossessed, but also of the attempt to warn the Calomares ranch ahead of the boys' coming which Morales had made, he began to wish he never had called Frank.

"Think of it," he said to Dave Morningstar, after explaining the situation. "In all likelihood all that clash of conversation in the air put them on guard at the Calomares ranch. They were led to suspect all was not well. And then when the boys landed they were captured. That can be the only reason for our failure to hear from Bob and Jack."

"No, something has happened to them," he said. "Oh, I was a fool to let them go. I'll never forgive myself. If only they were not injured. If only they were merely made prisoner, I——"

But Dave took up a headpiece and began adjusting the tuner knob. In a moment he tapped Mr. Temple on the bowed shoulder.

Similar anxieties to those ruling at the Hampton radio station had been in control at the cave during the evening hours.

Frank had been frightfully anxious as the hours wore on with no word from the boys. The flight to the ranch was a short one of only fifty miles. Surely, if they had been successful, Jack and Bob long ere this would have called him by radio in accordance with their agreement.

The poor boy stamped up and down the cave in such a fret that Tom Bodine and Roy Stone made repeated efforts to calm him, but without success. They began seriously to fear the effect of this anxiety upon his system, already fevered by the several hard fights through which he had gone in the last thirty-six hours.

Mr. Temple's call had done nothing to assuage Frank's anxiety. If anything it had increased it. As he put aside the headpiece, he looked so woebegone that Tom Bodine went up to him and laid an arm over his shoulder.

But before he could proceed, Frank's glance caught the light flashing in the signal bulb, and he leaped to the headpiece and microphone with a glad cry.

At the cave in the mountains of Old Mexico and at the Hampton ranch across the border in American territory, these welcome words uttered in Bob's well-known voice were received with delight. Across mountain and desert sped the message by radio. Modern science making possible the utilization of the forces of the air brought this quick relief to an anxiety that otherwise would have continued for hours at the least, until Bob and Jack could have flown back to the ranch.

But neither Mr. Temple nor Frank took that thought into consideration. To them radio telephony was an accepted fact, part of their daily equipment for carrying on life.

What filled their minds to the exclusion of all else was, at first, a sense of gratitude and thankfulness for the lucky outcome of the adventurous mission of the two boys, and, in the second place, a desire to learn the details.

"Now don't interrupt, Frank," said Bob. "Just listen while I talk to father, and you can hear all about it."

Under this admonition Frank ceased the flood of eager questions he had loosed and confined himself to listening. As the story of the remarkable series of adventures undergone by Jack and Bob at the Calomares ranch poured through the air, however, Frank, at times, could not curb his quick tongue, and many an exclamation he let slip. His hand, placed across the mouth of the microphone, however, acted to prevent these exclamations from interrupting the flow of Bob's explanation.

When Bob had finished his account, Jack took a turn. And at the recital of his adventures, Frank began to laugh. Removing his hand from the microphone, he interrupted his chum with the question:

Jack, who at the moment, was telling of the part played by Senorita Rafaela, blushed violently and grew indignant. Bob, standing near, looked at him speculatively. Was old Jack hard hit by that little Spanish beauty? Ordinarily, Jack would have answered Frank's joking in kind. But to grow indignant! Bob feared his chum was smitten.

For a long time the three-cornered conversation was carried on through the air, Mr. Temple and Frank both being eager to hear every detail and compelling Jack and Bob to repeat their stories several times.

Finally, drawn by the long absence of the boys, Mr. Hampton appeared at the radio station accompanied by Don Fernandez himself, and he and Mr. Temple held a brief conversation.

At length it was decided that the next day Mr. Hampton, with Bob and Jack, would fly back to the Hampton ranch in New Mexico. Frank, Tom and Roy Stone were to ride for the border at the same time, after another night's sleep at the cave. Morales and Von Arnheim, to whom Don Fernandez spoke personally, were apprised of the turn of affairs, and were told to stay at the cave, which was plentifully provisioned, until a relief party from headquarters could reach them with mounts.

Then "good nights" were said, and at their three different points our respective characters retired for the night, well pleased with the outcome of their adventures.

CHAPTER XXXII

MORE ADVENTURE AHEAD

Jack clasped the sprightly Spanish girl's hand, reluctant to release it. It was noon of the next day. Brilliant sunshine flooded the landing field of the Calomares ranch. Bob already had clambered into the pilot's seat of the airplane. Mr. Hampton stood to one side, exchanging farewells with Don Fernandez.

"No," said Jack, grinning. "But," he added, significantly, "I may come back—to capture one of its inhabitants."

Low though his tone was, the words reached the ears of Donna Ana, the ever-present duenna, and she glared at him. This was no way for a brash young Americano to be speaking to the daughter of the great Don Fernandez. Jack caught the glance and laughed. He turned to the duenna and extended his hand.

The wizened old duenna was nonplussed. She did not know whether to resent this pleasantry or be gratified by it. Mechanically she accepted Jack's extended hand.

At that moment, Bob called to him. Jack turned. Mr. Hampton already had entered the airplane. They were waiting for him. Once more he seized Rafaela's hand.

"Remember," he said, so low that only her ears could hear his words, "you haven't seen the last of me."

Then Jack climbed into his seat. A mechanic started the propeller, the machine began to bump over the ground, and presently it was in the air and climbing.

Bob spiralled upward until they were high above the ranch, and the figures below seemed little manikins. Jack believed he could distinguish Rafaela waving a lacy handkerchief, and leaned far over the side to wave in reply.

Then they were off, zooming through the air, straight as an arrow for the international boundary and the Hampton ranch beyond. The flight was brief. Bob covered the distance of 150 miles in considerably less than two hours.

"Look here," he said to his father, after greetings had been exchanged, and the latter had thumped his big son so hard and often that Bob dodged when further "love taps" came his way. "I'm not going to stay here to be pounded into a jelly. Tell you what, father, that's a long ride up here from the cave. Frank started early this morning, but he cannot arrive for another day. Suppose I go back and pick up him and Roy Stone, and leave Tom to bring in the horses?"

Reluctant though he was to let his son depart so soon after regaining him, Mr. Temple was persuaded, and Bob set off. Far down in Old Mexico, back trailing over the route they had followed in entering the country, he saw three horsemen leading a fourth animal, and on approaching close, saw they were his friends.

Landing near them, Bob called an explanation of his mission. Roy Stone demurred at the proposal.

"Much obliged for the offer," he said, "but I'll ride along with Tom Bodine, if it's all the same to you. I'm in no hurry to get anywhere, and you fellows will be having your own reunion at your ranch. Take your chum with you, but leave Tom and me. We'll be in with the horses sooner or later. Each of us will have a spare mount now, and it'll be an easy trip. Anyhow, I never did like those airplanes."

"Same here," said Tom Bodine, staring with awe at the machine. "You couldn't get me in that thing on a bet."

Frank, accordingly, relinquished the reins of his horse to Tom Bodine, and with "good-byes" to his friends clambered into the airplane with Bob. Roy Stone obligingly spun the propeller, an accomplishment with which his association with Von Arnheim had made him familiar, and once more the plane soared upward and headed across the border.

At the ranch that night it was a jolly party that gathered around the board, with Mr. Hampton, Mr. Temple and the three boys. Gabby Pete, talkative as ever, was bursting with desire for information about all their adventures. He had prepared a surprisingly good dinner in honor of the occasion.

Rollins alone was not present. When told of Mr. Hampton's impending arrival, he had begged Mr. Temple to let him go to a distant oil well for several days until Mr. Hampton could be informed in detail of his treachery in the past and the reason for it. This Mr. Temple had agreed to.

Back and forth across the table flew the conversation and, when the meal was at an end, all continued to sit around the table until a late hour.

During the weeks that followed Bob and Frank spent many enjoyable hours rambling on horseback over the surrounding country and taking more extended trips by airplane. The love for the country of which Jack had spoken on arrival, seized them, too. The bright hot days succeeded by cool nights—for in New Mexico the air cools immediately upon the setting of the sun—appealed powerfully to boys reared on the seacoast. The absence of raw winds and fogs especially appealed to them. The weather was something which could be counted upon. Every day was fair.

So passed the weeks, with the boys under Jack's pilotage travelling far and wide, scouting through the mountains to discover new beauties of scenery, making visits to the ancient Spanish ruins at Santa Fe, attending a rodeo at Gallup, to which came cowboys and cowgirls from a vast stretch of territory to perform hair-raising feats of horsemanship and exhibit well-nigh miraculous skill with the lasso.

A month after their advent, and when their summer vacation was not yet half spent, Mr. Temple at dinner one night announced that before ending his prolonged vacation from business—the first he had taken in ten years—he planned to go to San Francisco to consult with the manager of his western exporting office.

"Why, father," said Bob. "I've always wanted to see the city by the Golden Gate, and I know the fellows feel the same way about it. What do you say to taking us with you? We won't get in your way. And you can drop us here on your way back East."

Smilingly, Mr. Temple gazed at the faces of the three eager boys. Jack and Frank enthusiastically echoed their chum's appeal.

"Well, it's a good deal changed from the days of the Forty-Niners," said Mr. Temple, smiling. "You may have your hopes too high, and may be disappointed."

"Oh, come now, father," said Bob. "If you're going to be there only a week, it'll be worth while for us."

"Well, that's the length of time I planned to stay," said Mr. Temple, thoughtfully. "But I'll be pretty busy while I'm there. Do you boys feel you can keep out of mischief if left to yourselves?"

"I reckon they can, Temple," he said. "They saved the day for me. I'm beginning to think they are a pretty self-reliant lot. If you can see your way to doing so, take them along. The trip will be a fine experience."

"All right, boys," said Mr. Temple. "But you'll have to leave your airplane. If you are going to see San Francisco, you can't do it very well by airplane. And, anyhow, I wouldn't care to see you tackle the Rockies."

"All right, father," agreed Bob. "We'll be too busy seeing the sights to want the plane, anyhow. When do we start?"

With this we take leave of the three chums, whose adventures on the Mexican border have come to so successful a conclusion. But in the next story of "The Radio Boys on Secret Service Duty" we shall follow their further adventures after they reach the city by the Golden Gate—adventures fully as thrilling as those on the Mexican border, in which they become drawn into the plots of an international gang of smugglers engaged in bringing Chinese coolies into the United States in defiance of the Exclusion Laws.

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