CHAPTER XVIII.

BERT HOLTON, SPECIAL OFFICER.

Standing in the doorway was a slim, wiry, alert-looking man of twenty-eight or thirty, dressed in a dark, serviceable suit, with leather leggings. He leaned carelessly against the sagging doorpost, a slight smile on his smooth-shaven face, watching them with keen, snapping black eyes.

“Is this your monoplane?” Dick asked quickly.

“I don’t know anybody that has a better claim to it,” the stranger answered promptly.

As he glanced again at the aëroplane, Merriwell gave a sigh of relief. This, then, was what they had seen the night before, and he had quite misjudged Randolph. The scientist had probably never left his house.

Dick had been so anxious to think the best of Frank’s friend that he was rejoiced beyond measure to believe that his suppositions to the contrary were wrong. Then he remembered the lie Randolph had told him. That, at least, had not been disproved.

“You gents seem mighty interested in my little bird,” the slim man remarked as he stepped forward and joined them. “Might I inquire if you’ve happened to see another one around here lately?”

Dick gave a slight start.

“Why do you ask that?” he questioned.

The stranger hesitated.

“I might as well tell you the truth,” he said at length, with a slight shrug of his shoulders. “I’m about at the end of my rope, and you’re not apt to help me any unless you know what you’re doing. My name is Holton--Bert Holton. I’m a special officer from Washington. For about five months we’ve been trying to run down the cleverest gang of diamond smugglers that ever tried to beat Uncle Sam. Got on to ’em first through one of our agents in Europe. Glen is certainly a smart chap; I don’t know how he smells out some of these cases, but somehow he got wind of a party that was having a big bunch of rough diamonds cut in Amsterdam. Didn’t know where they came from, but he got suspicious at the amount of stones the duck had and wired us when he took passage direct to Canada.

“We had men on hand to meet the gent, and he was shadowed wherever he went. He didn’t make any try to cross the border, but took the Canadian Pacific direct to a farm he had about two hundred miles the other side of Winnipeg. It was a good seventy-five miles from the State line, and the fellows didn’t have much difficulty shadowing him. They had their trouble for their pains, though. The old duck didn’t stir away from his farm for six weeks, and then what do you suppose he did?”

Merriwell smiled at the fellow’s earnest manner.

“Give it up,” he answered. “What was it?”

“Took ship to the other side and went direct to Paris. This time the boys over there were ready for him. He stayed two days at one of the big hotels and then went to Amsterdam. While at Paris he was seen talking with a big, rough-looking fellow who looked like a Dutchman. After Carleton--that was the name of the Canadian guy--left Paris, this Dutchman was followed until he got aboard a steamer bound for South Africa. At Amsterdam, Carleton trots right off to his diamond cutter, leaves a lot of rough stones with him, and sails for home with another bunch of cut and polished sparklers. It was a cute game, and Heaven only knows how long they’d been playing it.

“Well, sir, that chap had the whole department guessing. Try as they would, they couldn’t catch him with the goods. Of course, they couldn’t touch him on British soil; he had a perfect right to have bushels of diamonds there if he wanted to. But there was a bunch of inspectors watching him and all his friends, that pretty near started a riot among the people thereabouts. Nothing doing, though. He never went near the line; and if he had, it wouldn’t have done him much good, with the country a wilderness for hundreds of miles.

“Finally I was put on the job, and after the fellow’s third trip across the pond--he must have brought back half a million in diamonds, all told--I got wise to their little game. It certainly was the slickest thing you ever heard of, though I’d been kind of expecting something of that sort ever since airships began doing stunts in the air.”

A look of intense interest leaped into Merriwell’s face.

“What!” he exclaimed. “You mean that they brought the diamonds across the line with an aëroplane?”

“That’s what,” nodded Holton. “Of course Carleton wouldn’t let us on his property, so we couldn’t look around much. He had a lot of fierce dogs, and the place was full of man traps and all sorts of riggings like that. But I found out afterward that the whole side of one of his barns was removable, so when the aëroplane came at night it landed in the upper part of the barn and nobody was the wiser. He’d load up with the sparklers and slide out the next dark night that came along. The only way I got onto the game was by keeping watch all night at the edge of the farm, and at last I saw the thing swoop down and land somewhere among the buildings.

“I beat it back home and had a talk with the chief, who decided that the only way to catch them with the goods was in another aëroplane. You see, nobody had the least idea where he went after he crossed the border. So he bought a good model on the quiet, and I took some lessons running it. In a couple of weeks I could handle it pretty fair, and it was shipped to Winnipeg and assembled there. I had the dickens of a job finding a place near Carleton’s to keep it, but finally located an out-of-the-way barn that I rented and fixed up. When the machine was installed there, I went back to watching again.

“I hadn’t been at it long before he slid in one night, and don’t you believe that I wasn’t ready for flight then. He stayed over one night, but the next he was off just after dark, and me after him. I thought he was never going to stop flying. We made about fifty miles an hour, and by daybreak I figured we must be somewhere in Wyoming. He landed in the mountains just as the dawn began to break, and I dropped down a few miles away.

“At dark I was ready again, up in the air circling around. He made for this place straight as a string, swooped down a little after midnight, and then blamed if I didn’t lose him. Seemed as if the earth had just opened and swallowed him up, and I haven’t seen hide or hair of him since. You see, I’m up against it for fair, and when one of you gents says, ‘it’s _the_ airship,’ like as though you’d seen one around here before, I thought perhaps you’d glimpsed the other fellow’s, and maybe you could help me out.”

As he finished, the young inspector looked inquiringly from one to the other of the two Yale men. He retained his air of careless nonchalance, but only by a palpable effort. Deep down underneath it there was an expression of anxious appeal in his eyes. It was quite evident that he was, as he had said, “up against it for fair”; otherwise he would never have confided so promptly in two total strangers, and Dick had a very strong inclination to help him out. But could he?

Not being in the least slow, Merriwell had at once sensed the entire situation. The mystery of Scott Randolph was a mystery no longer. Bert Holton’s straightforward story had cleared it up completely. He was a smuggler, pure and simple. Amazingly clever, to be sure, and conducting his operations on a huge scale, he was none the less a smuggler, and his extremely plausible story of manufacturing diamonds had been made up out of whole cloth to cover his real doings.

A faint flush mounted into Dick’s face as he realized how he had been duped, and for a moment he would have given a good deal to be able to put this clever officer on Randolph’s trail. But could he? There was that unfortunate word of honor which he had given and which he could not break. Moreover, such was Scott Randolph’s extraordinary charm of manner and likableness that, in spite of everything, Merriwell did not quite like the notion of turning him over to the law.

It was Buckhart who solved the problem. Bound by no promise of silence, knowing nothing of the diamond hoax, his mind was so full of what they had seen the night before that the consequence of his words did not occur to him before he blurted them out.

“Why, sure, bucko,” he said quickly. “We saw an airship fly out of these very mountains last night.”

A gleam of excitement leaped into Holton’s keen eyes.

“You did?” he cried. “What time? Which way did it go?”

“About eleven o’clock,” the Texan answered promptly, “It flew northward.”

Holton made a despairing gesture with his hands.

“He’s gone back to Carleton’s,” he exclaimed. “By George! He’s given me the slip! If I’m not the worst kind of a lunkhead!”

“I reckon not,” Brad put in quickly. “He came back again in about thirty minutes.”

“Are you sure?” Holton asked doubtfully.

“Yep; we saw it plain. He must have gone twelve or fifteen miles, and then we saw him flash some lights like signals. Pretty quick after they stopped the machine came back again to the place where it started from.”

“And where was that?” the officer asked eagerly. “Say, Jack, haven’t you any idea at all who it belongs to?”

“We thought it was Randolph,” Buckhart returned promptly. “He’s the fellow that lives in that stone house with barred windows and a steel door.”

“Never heard of him,” Holton said quickly. “I’m a stranger here, you know. It sounds good, though. How do you get to it?”

“Go down to Bonnet Trail and walk toward Denver,” the Texan answered. “In about half a mile you come to a narrow road on your right. Randolph’s place is at the end of that road, not more than a quarter of a mile----”

He stopped abruptly as his eyes fell on Dick’s face. It was calm and impassive, but there must have been something there which made the big Westerner think that perhaps he had been saying too much. He hesitated for a moment and then went on rather lamely:

“Of course, I’m not at all certain that it was his aëroplane. It came from near the house, but it might have belonged to some one else.”

“All the same, I think I’ll look the gent up,” Holton remarked. “It’s the only clue I’ve had, and it sounds pretty good to me.”

There was silence for a few moments, then Merriwell glanced suddenly at the special officer.

“Are these monoplanes hard to manage?” he asked.

“Why, no, not very,” Holton answered. “The control is very simple, once you’ve got the hang of it. I’d rather manipulate a monoplane than a biplane any day. Ever been up in one?”

“No, but I’ve always wanted to,” Dick answered. “I’ve done something with gliders at college. The principle is pretty much the same, isn’t it?”

“Exactly. Some people seem to have the idea that you get along by flapping the planes like the wings of a bird, whereas they are almost immovable. Of course, they can be deflected or depressed according as you rise or descend, but the only thing that keeps you going is the revolution of the propeller. If the engine should stop, you’d be turned into a simple glider. Even then, you wouldn’t go down with a smash, but by a proper manipulation of the plane and rudders, you could glide on a long, easy curve, and could almost choose your own spot for alighting.”

“I see,” Dick said. “The two rudders are controlled by levers, I suppose.”

“Sure.”

Holton stepped to the rear of the aëroplane and Merriwell followed him interestedly.

“Here’s the horizontal rudder,” the officer explained, pointing out the two smaller, parallel planes which were attached to the extreme end of the light frame that protruded from the body of the aëroplane like an enormously long tail. “By a system of wires and pulleys, it is connected with the lever next to the seat. You pull that lever forward and the rudder is thrown upward, inclining the big plane so that the air strikes it underneath and drives it upward. In the same way when the lever is thrown back, the plane is deflected the other way and the machine descends. In flying it’s always necessary to give the plane the least possible upward inclination, so as to get the full benefit of the air striking against it.”

Merriwell nodded understandingly.

“This rudder above it is the vertical rudder, I suppose,” he said. “It looks exactly like the rudder on a boat.”

“It is like it, and acts the same way. You use that in making a turn, and it is controlled by the lever next to the other one. Pushed forward, it turns the rudder to the right, backward, to the left. When you’re flying straight ahead it’s kept upright, of course.”

He pulled a worn, red leather notebook from his pocket and slipped off the rubber band.

“It’s this way,” he went on, as he drew a simple diagram on one of the pages.

Dick bent his head over the book, while Holton explained in detail the principle of rudder control, illustrating his meaning with rough sketches. When he had finished, the Yale man straightened up and looked again at the machine.

“It’s quite as simple as I thought,” he said slowly. “I believe I could operate it with a little practice. Eight-cylinder engine, isn’t it?”

“Yes, and it’s a little beauty,” the officer said enthusiastically. “I’ve never had a bit of trouble worth speaking about. It’s a French make and only weighs a fraction under three pounds per horse power. It drives the crank shaft, which runs under the seat out to the propeller in front.”

Dick examined the engine closely. It was beautifully made and took up a surprisingly small space.

Seeing his interest and his quickness of comprehension, Holton, who was an enthusiast, pointed out the various parts, and at the end of half an hour the Yale man understood it thoroughly.

“I suppose you’d have to have some kind of a start to make an ascension from here, wouldn’t you?” he asked.

“All you’d need would be some one to loosen the anchor rope which I’ve tied to that tree over there, and give you a good, running shove,” Holton said. “Of course, you’d get your engine going first and the plane and horizontal rudder inclined properly. You see, with these light pneumatic wheels underneath, it’s no trouble at all for one man to give you the necessary starting velocity. Sometimes you don’t even need that, but can start yourself, especially if you’re on a slight incline. That’s the sort of place I usually try to pick out when I come down.”

He hesitated for an instant. He was plainly an enthusiastic aviator.

“I’d like to make a short ascension and show you how it works,” he said, “but I don’t dare to. That fellow doesn’t know I’m anywhere around, but if I went up now, he’d spot me in a minute and be on his guard.”

“Of course he would,” Dick agreed readily. “Perhaps, though, after you’ve nailed him, you’d be willing to give us an exhibition.”

“Sure thing,” Holton grinned. “Come out and see me to-morrow. Maybe there’ll be something doing by that time.”

“I will,” Merriwell returned promptly.

Then he turned to Buckhart.

“I guess we might as well be on our way, old fellow,” he said quietly. “Now that we’ve mastered the principles of flying, there’s nothing to keep us here. Good-by, Mr. Holton.”

“By-by, fellows,” the officer said warmly as they started down the slope. “Much obliged for the tip.”

“Don’t mention it,” Brad called back.

They had almost reached Bonnet Trail where they had left the car, when he stopped suddenly and looked at his companion.

“Say, what about Randolph’s aëroplane that we started to find?” he inquired. “I never knew you to give up anything as quick as that, pard.”

Dick smiled.

“I gave it up because I didn’t want to find it,” he returned. “Randolph’s a piker, all right, and deserves to have this fellow Holton land on his neck; but I’d rather not have anything to do with his capture.”

The Texan grinned broadly.

“That’s why you looked so blamed serious while I was chattering away like a dame at a pink tea,” he remarked. “I sure put my foot into it, didn’t I?”

“Not a bit of it,” Merriwell returned. “I was afraid you were going further and put him wise to all this talk about diamonds and that sort of thing. There seems to be no question that he’s the smuggler Holton is after, but somehow I’d like him to have every chance he can. We were his guests last night, and he was mighty nice to us; besides, he used to be a friend of Frank’s, and---- Oh, well, let’s just put him out of mind. If he gets pinched, all right; if he gets away it will be equally satisfactory.”

This proved to be easier said than done. After a leisurely luncheon the two friends took the car again and went for a long drive out toward Castlerock, from which they did not return until past six. It is safe to say that half an hour did not pass during the entire afternoon in which one or the other of them was not thinking of Scott Randolph and wondering whether Holton had found him, or whether he had escaped, or what had happened.

Returning to the hotel, Dick drove around to the garage very slowly; and, instead of running the car in, he slid up to the curb and stopped. Then he turned in his seat and eyed Buckhart questioningly without saying a word.

“Well, why not?” the Texan inquired suddenly, apparently apropos of nothing on earth. “I’m sure curious to know how it all came out.”

Dick laughed as he guided the car slowly down the street again.

“Evidently we haven’t either of us been successful in getting Randolph out of our heads,” he said. “We’ll just take a run out and see if I can get hold of my pocketbook this time.”

The swift twilight was just beginning to fall as they hurried up the narrow track and reached the open space before the stone house.

If they expected to find any signs of life about the place they were disappointed. The same grim, menacing wall of stone confronted them, from the same desolate, shadowy background. The steel door was as tightly closed as ever, the barred windows as expressionless. But wait! Were they quite the same?

Dick’s eyes were fixed on the end window on the second floor.

“Take a good look at that shutter up there, Brad,” he said in a low tone. “It looks to me as though it were open about an inch, but this dim light is beastly deceptive.”

The Texan studied it for an instant.

“You’re right,” he said quickly. “It is open the least bit. Some one’s been there since this morning, all right.”

Merriwell stepped to the door and hammered loudly on it.

Five minutes passed in unbroken silence. Then he beat another thunderous tattoo on it, long and loud.

Still no response. The house was silent as a tomb.

The Yale man stepped under the window and looked keenly up at it. Was it possible that some one was watching them through that tiny crack? If so, the rapidly falling darkness hid him effectually. With a sigh of regret, Merriwell stepped back, his foot striking a small object on the ground.

Instantly he pounced on it and held it up.

It was a small, worn notebook, bound in red leather and kept together by a rubber band.

For a moment both men gazed in tense silence at the commonplace thing. Then Dick slipped off the band quickly and opened the book.

As his eyes glanced swiftly over the first page, even the semidarkness did not hide the sudden pallor which spread over his face.

“Heavens above!” he breathed in a horror-stricken voice.

“What is it, pard?” Brad asked anxiously. “What has happened?”

Unconsciously Merriwell clenched one hand tightly and his teeth came together with a click.

“Randolph has shut Holton into the air-tight room,” he said slowly.

“What!” gasped the Texan, as though unable to believe his ears. “Deliberately left him there, you mean?”

“Yes,” Dick said in a hard, dry voice. “Listen.”

He bent over the notebook, barely able to distinguish the scrawling words, in the failing light.

“‘He caught me by a trick,’” the Yale man read slowly. “‘Says he’s going to shut me in a room where the air will last two hours and no longer. If anybody finds this, for God’s sake get me out. I’ve only a minute to write this and throw it out of the window. Don’t waste a minute, but hurry. I can’t die like a rat in a trap. HOL----’”

The note ended in an irregular line as though the writer had been suddenly interrupted.

The Texan’s ruddy face was pale as death and in his eyes there came a look of horror.

“Two hours,” he exclaimed in a strange voice--“two hours to live!”

Dick threw out one hand in a gesture of despair.

“And those two hours may be up!” he cried. “No one knows how long ago this note was written!”