Tom, having so suddenly burst into the store, grabbed the man by the collar and whirled him about so that the two were face to face. It was Hankinshaw.

“What do you mean by that?” sputtered Hankinshaw, as he tried to wrench himself loose from the strangle hold that Tom had on him, his face fairly apoplectic with rage.

“It’s up to me to ask you what you mean by daring to bother this young lady,” responded Tom, in a low tense voice while his eyes glinted like steel. “He was annoying you, wasn’t he, Mary?”

“Yes, he was,” replied Mary excitedly. “And, oh, Tom, I’m so glad you came! But please, Tom,” she added more calmly, “don’t make a scene. Let’s get out of here as soon as possible.”

Tom relinquished his hold on Hankinshaw’s collar.

“You’re right, Mary,” he agreed. “His case can wait till another time. But it’s only your being here that saves him from getting the thrashing of his life.”

“Huh!” snorted Hankinshaw, who, while not quite as tall as Tom, was much bulkier and heavier. “That’s easy enough to say. Talk is cheap. What do you suppose I’d be doing while you were trying to mess me up?”

“Nothing much,” retorted Tom drily. “That will be enough from you, Hankinshaw. Give me your parcels, Mary, and I’ll see you home.”

“The nerve of you to lay your hands on me!” snarled Hankinshaw, who was getting angrier and angrier. “I’ve a good mind to have you arrested for assault and battery.”

“Try it,” recommended Tom. “It would be a good chance to show you up for what you are. Come along, Mary.”

“Gallant knight with his fair lady,” sneered Hankinshaw.

“What’s that?” exclaimed Tom, taking a step toward him.

Before the blaze in the young inventor’s eyes, Hankinshaw stepped back hastily. As he did so, his foot struck a box on the floor and he fell backward and went through the confectioner’s window. There was a crash of splintering glass, and the next instant Hankinshaw was on the sidewalk, surrounded by a litter of glass and a score or more of candy boxes that had been flung out with him.

“Oh, I do hope he isn’t hurt!” cried Mary, in a fright.

“I guess not,” replied Tom, as they hurried outside. “You go along, Mary, before a crowd gathers. I’ll stay behind to help him if necessary.”

The confectioner had rushed outside with them, in alarm both for his window and the man who had gone through it. Mary hastened on, while Tom and the store owner, a Mr. Wilkins, helped Hankinshaw to his feet.

To their relief, they saw that apart from a few scratches on one of his hands and the damage to his dignity, no harm had come to the bulky fellow. But his eyes were baleful as he glared at Tom. If hate could have killed, Tom would have been a dead man.

“I’ll fix you for this, Swift!” he declared venomously.

“You brought it on yourself,” replied Tom. “I’m glad though that you weren’t seriously injured. You’d better get back to your hotel before a crowd gathers. It wouldn’t be pleasant for you to explain just how you happened to go through the window. Don’t worry about the glass, Wilkins,” he continued, turning to the confectioner. “If he doesn’t pay for it, I will. And mind, Wilkins, not a word as to the young lady who was in the store at the time this happened.”

“You can count on me, Mr. Swift,” replied the storekeeper, reassured by what Tom had said about the broken window. “Nobody’ll get anything out of me.”

It was lucky that the accident had occurred at a time when most of the people of the town were at supper and the streets were almost deserted. Some had gathered, however, attracted by the crash, and more were coming, and to avoid questioning Tom went off quickly toward his home. Hankinshaw after a moment of hesitation started off for his hotel, not caring to have others see him in his awkward and humiliating position.

The first thing Tom did on reaching the house was to take up the telephone and call up Mary. There was a tremor in her musical voice as she answered.

“Oh, Tom,” she said, “I’m so glad to hear from you. I’ve been worried to death ever since I left you. Was the man badly hurt?”

“Only a few trifling scratches,” replied Tom. “The fellow got off better than he deserved. The last I saw of him he was hot-footing it for his hotel. What he’d like to do to me is a sin and a shame.”

“Do be careful, Tom,” urged Mary anxiously. “He had the look in his eyes of a sneak. I’m afraid that in some underhand way he may do you an injury. I’ve been worrying, too, for fear it may affect the business deal you have with him and his partners.”

“Not a chance,” laughed Tom. “He couldn’t back out now without being a loser, and he and his crowd are too canny for that. Not that I’d care a bit if he did. I’m half sorry we took the contract, anyway. If we hadn’t, this Hankinshaw wouldn’t be hanging around Shopton. But thank goodness the work is getting pretty well along now, and in a few weeks the contract will be completed. Then he’ll be nothing but a bad dream—perhaps I ought to say a nightmare. Don’t worry your pretty head any more about it.”

“But keep away from him all you can, won’t you?” pleaded Mary.

“I guess he’ll keep away from me,” laughed Tom. “But I’ll promise you, if that will make you feel better.”

Tom’s prediction proved correct. For several days Hankinshaw did not appear at all at the works. And even when he resumed his visits they were brief and less frequent than usual, and he avoided meeting Tom as much as possible.

In the meantime, the high board fence around a section of the grounds of the plant had been completed. Material of various kinds had been carried in and set up by a group of chosen workmen under the close supervision of Jackson. Gradually a structure arose that would have seemed strange to the eyes of the people of Shopton, though familiar enough to dwellers in the oil fields of California, Oklahoma and Texas.

Tom was building an oil derrick and getting together a full paraphernalia of cables, drills and other tools necessary in oil-well digging. Everything was on a miniature scale to save expense, for the structure was only designed to be temporary and would be demolished when the need for it had passed.

“Aren’t you going to a good deal of trouble and expense for this one job?” asked Ned, a little anxiously. “It won’t take much to eat up all the profit there is on this contract.”

“Don’t worry, old boy,” replied Tom. “If this one contract were the only thing concerned, this wouldn’t be necessary, for all we have to do is to follow the specifications of their plan. But I’m doing this for a different reason. This isn’t for the benefit of Thompson, Bragden and Hankinshaw, but for trying out something new for the Swift Construction Company. Do you get me?”

“Do you mean that you’ve hit on a new invention?” asked Ned eagerly.

“Something like that,” answered Tom with a smile. “Not that I’d call it an invention—yet. I’ve got a whole lot of things to work out in connection with it. But the idea I’ve struck seems feasible enough as far as I’ve gone. I’m getting rid of the technical difficulties one after the other, and the farther I go, the more convinced I am that I’m on the right track. But nobody knows better than you that there’s a long step between theory and practice. The thing that seems perfect in the study may prove to be a flivver in the field. That’s the reason why I’m rigging up this miniature oil-well outfit. I want to put my idea to a practical test. Maybe it’ll work. Maybe it won’t. If it doesn’t, I’ll discard it and hunt up something better.”

“Go to it, Tom, and good luck to you,” cried Ned enthusiastically. “I’d have bet my life you’d hit on something new.”

“Hold your horses,” cautioned Tom. “The best laid plans sometimes ‘gang agley.’ I’m a long way off yet from certainty. But I’m far enough along to justify this expense to find out whether I’m right or wrong.”

So the work went on until the structure was complete, and any one who entered the gates of the carefully guarded enclosure would have rubbed his eyes and wondered how long it was since Shopton became an oil field.

The most prominent object was the derrick, or rig, a framework tower wide at the bottom and tapering off at the top. This was for the purpose of carrying two pulleys, the crown pulley in the center and the block through which the sand line ran. Over the crown pulley ran the cable by which the drilling tools were suspended or lowered or raised. At one side of the rig was the bull wheel, or windlass, upon which the cable was wound, and at the other was the walking beam, a heavy timber hung in the center so that it could undulate up and down.

Then there was a choice collection of drilling tools, consisting of a bit, an auger-stem, a sinker bar, a rope socket and jars, all of which were strung together and suspended from the crown pulley by the cable. In addition there were the wrought-iron casings for the lining of the projected experimental well. Nothing essential had been overlooked, and before long Tom found himself in a position to begin the tests on which he was counting so much.

Ned in the meantime had been having troubles on the accounting end. At the expiration of the two weeks when it was stipulated that the second five thousand dollar payment should be made, the check was not forthcoming. Ned telegraphed to Thompson and hunted up Hankinshaw. Both of them put the blame on Bragden, who at the time, they stated, was on a short vacation from which he would return in a few days, when the matter would be promptly adjusted. This, however, did not satisfy Ned, who recognized the familiar tricks of “shoestring” concerns, and he proceeded at once to “put on the screws.” But it was only when he threatened immediate stoppage of work on the contract that the draft he had sent through was finally honored.

“I told you they were as slippery as eels,” Ned reminded Tom, as they looked at the cashier’s check whose delay had been so annoying.

“Yes, and perhaps you wouldn’t have been so far wrong if you had added that they were as crooked as corkscrews,” replied Tom.

“Bless my premonitions! I’m afraid you’re right,” exclaimed a voice behind them.

Tom and Ned looked up, a little startled, and saw their eccentric friend, Mr. Wakefield Damon.

“Bless my gum shoes!” exclaimed Mr. Damon, wiping his glasses and settling into the chair that Tom pulled over for him. “I came in on you like a thief in the night, and by a coincidence I hear you talking about thieves.”

“Oh, I wouldn’t want to put it as strongly as that,” said Tom, with a laugh. “But all the same the actions of that oil crowd don’t seem to be those of responsible business men. We’ve been having no end of trouble with them, one way and another.”

“I’m afraid perhaps I made a mistake in introducing them to you,” said Mr. Damon, with a slightly worried look. “Thompson was the only one of them I knew, and even with him my acquaintance was slight. By the way, did you get that second payment? Ned, here, was telling me that they seemed to be trying to sidestep it.”

“It came in to-day,” replied Tom. “But we had a heap of trouble in getting it. Here it is,” and he handed it over for his friend’s inspection.

Mr. Damon scrutinized it carefully and heaved a sigh of relief.

“Well, that puts you on easy street, anyway,” he said. “They’ll have to come across with the rest now to save what they’ve already invested. But I’m afraid somebody else is in for a trimming.”

“What do you mean by that?” inquired Tom, with quickened interest.

“I heard something when I was on my last trip to New York that set me thinking,” replied Mr. Damon. “I dropped into one of the clubs as the guest of a friend of mine who is a member, and among the people to whom I was introduced was a large Texas oil producer. Of course, that interested me at once, apart from the fact that he was a most entertaining talker. He told me a lot about his own experiences there, and in the course of the conversation got going about the many “wild-catters” that infest the oil fields.

“You know the wild-catter is to the legitimate oil man very much what the bucket-shop keeper is to the solid Wall Street broker. He hates him as he does ivy poison. The shady tricks in which the wild-catter indulges cast a stigma on the whole oil-producing business.

“Well, this man, in giving me some illustrations of wildcat methods, happened to mention the name of Thompson. Said he was one of the most suave and polished individuals that roamed over the oil fields.

“I didn’t let on that I knew any one of that name, but from the description he gave me of his personal appearance and manners, I feel sure that it’s this fellow you’re making this material for. I led him on to tell me what he knew of him, and if what he said is true, this Thompson ought to have his picture in the rogues’ gallery. Not that he ever will probably. He’s too shrewd for that. Always manages somehow or other to keep just within the law.

“Among other things, this new acquaintance of mine said that he’d heard that Thompson and his partners were trying to put something over on an old blind man who owns a likely property at Goby, I think it was, close to one of the big gushers that has come in recently. The old man didn’t want to sell or lease, and the Thompson crowd were determined to make him. Just how they were going to bamboozle him or coerce him, my informant didn’t know, but he had heard enough before he left to be sure that some shenanigan was on foot. Said he’d bet a hundred dollars to a plugged nickel that before many moons had passed the gang would have the property and the blind man would find himself buncoed.”

“So that’s the kind of fellows they are!” exclaimed Tom hotly. “If I weren’t held by my contract I wouldn’t do another jot of work for them.”

“Oh, well, it isn’t a dead certainty that that Thompson and our Thompson are the same man,” said Mr. Damon. “It’s a common enough name, as far as that goes.”

“Still, I think they’re identical,” insisted Tom.

“At any rate, you’ll be through with the job soon and then you’ll be rid of them for good and all. By the way, how’s the work coming on?”

“All right,” replied Tom. “Unless something unforeseen happens we’ll be through on schedule time.”

“What’s that thing on the grounds that looks like a derrick?” asked Mr. Damon. “It wasn’t there when I went away. Seems to have gone up almost over night, like Jonah’s gourd.”

“Oh, it’s a contrivance that I had built to test an idea of mine,” answered Tom.

At once Mr. Damon was after the hint like a terrier after a rat.

“Invented something new?” he asked eagerly.

“Not quite yet,” replied Tom, with a smile. “But I’ve hit on an idea that may amount to something when I’ve worked it out more thoroughly.”

“Good for you!” cried Mr. Damon enthusiastically. “I knew you wouldn’t be at this thing long before you struck something that would make anything that had gone before look like thirty cents. More power to you, my boy. What does your father think of it?”

“It hits him hard,” replied Tom. “I’ve gone into the thing pretty thoroughly with him and I’ve benefited a lot by his suggestions. He thinks it will mean an immense saving in time, expense and man power. So far, we haven’t run up against any obstacle that seems insurmountable. Still, you never can tell till it actually gets to working. It may turn out to be a flivver after all.”

“Bless my modesty!” snorted Mr. Damon unbelievingly. “Hear Tom Swift talk about flivvering! That’s one thing he’s never done yet.”

“There’s got to be a first time for everything,” bantered Tom.

“It’ll be a long time coming,” retorted Mr. Damon. “One thing I’m certain of,” he went on; “and that is you’ll have a mighty fine market for your invention when you get it perfected. You’ll have all the big companies bidding against each other to get hold of it. I tell you, my boy, there’ll be a fortune in it.”

“Let’s hope so,” said Tom. “But the pot of gold is still at the foot of the rainbow and it may be a long tramp until I reach it.”

Although Tom expressed himself in this cautious way, he felt quite certain in his own heart that he had hit upon a great invention. This concerned itself with the drill with its sharp cutting edge, or bit. Up to that time dependence had been placed upon having a hard tempered edge that cut into and splintered the rock by its sharpness, its weight and the distance from which it fell.

This was much. But Tom’s theory was that where there was much there could always be added more. Suppose a circular motion could be given to the bit at the moment of contact and the bit itself so shaped that in addition to the crushing power given by the weight and fall there would be a grinding, scooping movement that would eat into the very heart of the soil or rock, making each stroke vastly more efficient. If he could double its effectiveness, he would wipe out at once half the time required, half the wear and tear on the machinery, half the man power required, and vastly reduce the overhead expense. It would mean an incalculable saving to the oil industry, and to Tom himself it would mean a fortune.

His father agreed with him that he had hit upon an idea that went to the core of the matter. Then followed long days and nights of experimenting, until at last just as the dawn was lighting up the sky on one memorable morning Tom leaped from his seat in wild exultation and fairly shouted:

“I’ve got it! I’ve got it!”

After the first few minutes of jubilation, he went over his figures and diagrams again. Yes, if there was anything in mathematics, he had proved that the new drill and bit would do what was expected of them.

But the invention had first to be demonstrated in actual working, and he pushed forward energetically the work in his experimental plant.

About a week later he was working alone in the office, when, shortly after midnight, there was a knock at the door and Koku, whose night it was for self-imposed duty, entered. His eyes were rolling in agitation, and he had his fingers on his lips as though to impose silence.

“What is it, Koku?” asked Tom, somewhat startled by the air of mystery.

“S-sh,” warned Koku. “Man down at fence. Saw light.”

Instantly Tom was outside. He looked down toward the stockade that enclosed the experimental plant, but could see nothing.

“Guess you must have been dreaming, Koku,” he whispered.

“No,” said Koku. “Light come. Light go. There is now.”

Tom, too, saw a sudden gleam, as suddenly extinguished, that evidently came from a flashlight.

“Come, Koku,” he commanded, and moved down stealthily toward the fence.

Despite his great size, Koku was as light on his feet as a cat, and he made no sound as he followed in Tom’s footsteps. As silently as panthers they approached the fence.

Tom had slipped a revolver into his pocket as he left the office, as a matter of precaution, though he hardly thought he would have occasion to use it, and would only do so in the last extremity. Ordinarily his sinewy arms and powerful fists were a sufficient reliance. But there was no telling whether he would have to face an individual or a gang, and it was well to be prepared for any emergency.

One thing was certain. Whoever was there had no right to be there and could only have come for some evil purpose.

They had caught one more glance of a flash of light, but only one. Now everything was in absolute darkness. There was no moon and the ordinary blackness of the night was deepened by heavy clouds that presaged a storm. Tom could scarcely see his hand before his face, and it was only by reaching out occasionally and touching Koku that he knew the latter was close on his heels.

Tom had a powerful flashlight with him, but it was unnecessary to use it just then, for he was so familiar with every foot of the yard that he could have gone to the fence blindfolded. Besides, it was essential that the prowler or prowlers be kept in ignorance that their unlawful visit had been discovered.

Soon they were near the fence, and Tom caught one of Koku’s hands and drew him to him.

“Now, Koku,” he whispered, “I’ll go around one side of the fence and you go round the other until we meet. If you come across any one, grab him and hold him fast. But don’t call out, as that may warn others who may be with him. Hold him till I come up to you. No rough stuff. Don’t hurt him. Just hang on to him.”

Koku nodded and started round one side while Tom went in the opposite direction. There was not a sound to break the stillness. If there was any one about, he was acting with extreme caution.

Before long they had together completed the circuit and met.

“Did you see any one, Koku?” queried Tom, in a whisper.

“No,” was the reply. “But there is ladder against fence. Come.” And, turning, the giant, followed by Tom, went back to where a ladder was propped against the wall of the enclosure.

As Tom’s eye ran along its length, a flare of light stabbed the air but was quickly extinguished. At first it seemed to him like a faint gleam of lightning, but there was no thunder, and he realized that it had probably come from a flashlight.

Motioning to Koku to remain where he was, Tom went up the ladder. When he reached the top, he slowly and cautiously raised his head above the fence.

At first he could see nothing except the bulky derrick, which stood out as a formless blot against the blackness. But while he listened intently, he heard the clink of metal as though a hand were fumbling among tools, and an instant later there came another flash that revealed the figure of a man bending down with his back toward him.

Like a ghost, Tom slipped down the ladder. Then he laid the ladder flat on the ground, and, telling Koku to follow, went rapidly around to the gate of the enclosure.

He inserted his key in the lock, opened the gate slowly so that no grinding of the hinges should betray his presence, and then like two shadows the pair moved toward the derrick.

Again the clink of metal guided them, and soon they were within a few feet of the intruder, whose form was dimly visible.

Tom drew his flashlight from his pocket and touched Koku as a signal to be in readiness.

“Now!” cried Tom, and flashed his powerful light full in the face of Hankinshaw.

With a startled exclamation the latter started back, while at the same time his hand reached toward his hip pocket. But in that instant the giant Koku had leaped upon him and pinioned his arms behind his back.

Hankinshaw was a heavily built man and he struggled violently to free himself. But in Koku’s hands he was as helpless as an infant.

“Hold him, Koku,” commanded Tom, and went to the derrick. He took a lantern off a peg, lighted it and returned. He set the lantern on the ground and pocketed his flashlight. Then he passed his hands lightly over Hankinshaw’s clothes and drew from the latter’s pocket a revolver, fully loaded. He broke the stock, took out the cartridges and threw the now useless weapon on the ground.

During this process, Hankinshaw fumed and frothed and burst out in imprecations, to all of which Tom paid not the slightest attention.

“Now put him down on the ground, Koku,” directed Tom.

The giant obeyed, and Hankinshaw found himself sitting on the ground with startling suddenness. He started to get up, but Koku’s hands on his shoulders put him back with a force that jarred him and made his teeth chatter.

“Better stay put,” warned Tom. “That man of mine doesn’t know how strong he really is, and if he grabs you again you’re apt to get hurt. It will be healthier for you to stay right where you are until I tell you to get up. Get me?”

Hankinshaw evidently did “get” him, and sat still, his face black with rage.

“This is an infernal outrage,” he shouted. “I’ll get even with you, and don’t you forget it. What do you mean by assaulting me in this way, you and your man? I’ll——”

A long string of threats and expletives followed. Tom let him rave, looking steadily at him the while until beneath the blistering contempt in his eyes Hankinshaw faltered, sputtered and tapered off into a confused and incoherent snarl.

“Are you through now?” asked Tom.

“Not through with you, by a long shot,” snarled Hankinshaw.

“Whether you are or not, you’re going to listen to me now,” said Tom. “Unless,” he added, as though by an afterthought, “you’d rather have the police and the district attorney do the talking?”

At the word “police” Hankinshaw’s face blanched and his bluster dropped away.

“Because, you know,” went on Tom, “this is a police matter. I find you in the dead of night on my property after scaling a locked enclosure, handling my implements, and for all I know getting ready to carry them away. It’s as though I woke up in my room at night and found a burglar rifling my bureau drawers. The fact that he didn’t have time to get anything before I nabbed him wouldn’t prevent his being tried and convicted for burglary. I imagine that if I chose to hand you over they’d put you where the dogs couldn’t bite you for a while.”

Hankinshaw moistened his parched lips with his tongue.

“There’s no use talking that way,” he said, and there was unmistakable fear in his voice. “Why should I want to take anything away? And how could I if I did want to? They’re too heavy to handle. Do you think I’d walk off with your derrick?”

“Stop your stalling, Hankinshaw, and tell me the truth—that is, if you can,” commanded Tom sharply. “What were you doing in this enclosure at this time of night?”

“Why—why, I was restless and—and couldn’t sleep,” stammered Hankinshaw. “So I dressed and went out——”

“For a nice little moonlight stroll, I suppose,” interrupted Tom sarcastically, looking up at the lowering sky.

“I went out,” continued Hankinshaw, affecting not to notice the unbelief in Tom’s voice, “for a walk——”

“Taking your revolver along,” suggested Tom.

“That’s a habit I got down in Texas. One never knows down in the oil fields when it is going to come in handy. As I was saying, I went out for a walk and found myself coming in this direction. I happened to catch sight of the derrick——”

“Where did you see it from?” asked Tom.

“From the road, of course,” answered Hankinshaw.

“You caught sight of the derrick from the road three hundred feet away on a night when you couldn’t see anything ten feet ahead of you?” exclaimed Tom. “But go ahead. You interest me strangely.”

“I don’t mean exactly that I saw it,” said Hankinshaw, in confusion. “But I’d seen it in the daytime, and being so near it I suppose the thought of it came into my mind. Just from curiosity, I thought I’d come over and see what it was like. I didn’t think any one would mind. Didn’t know there was anything especially secret about it.”

“Didn’t suspect that even when you found the gate was locked, eh?” queried Tom.

“No,” affirmed Hankinshaw brazenly. “I was turning away when I stumbled against a ladder that some workman had left in the grass. That put it into my mind that I could get a squint at the derrick after all, and on the impulse of the moment I put it up and climbed over the fence.”

“How lucky it was that you just happened to have a flashlight along,” said Tom. “I suppose carrying flashlights is another habit you got down in Texas.”

“Yes,” returned Hankinshaw. “You have to travel around a good deal at night there, and you never know when you may need one. But now I’ve told you the whole story. I suppose I was trespassing, and I’m sorry now I did it, seeing the way you look at it. But you’re just making a mountain out of a molehill.”

“I imagine a burglar might say the same thing,” replied Tom, and his tone was so like steel that Hankinshaw visibly winced. “Now listen to me, Hankinshaw. I don’t believe a word of what you’ve been saying. It’s a falsehood from beginning to end. You deliberately committed a crime to-night, and you know as well as I do what chance you’d have if you told a fairy tale like this to a judge or jury. All I’d have to do would be to telephone to police headquarters and you’d be under lock and key in a hurry. But I’m not going to do that.”

An expression of immense relief came into the rascal’s face.

“Oh, it’s not out of any consideration for you,” Tom assured him. “It’s partly because I don’t want any scandal that would worry my father; in his present feeble state of health. Then, too, I’m too busy just now to take the time to prosecute you and send you where you belong. But don’t think for a moment that this ridiculous story of yours has imposed on me. You came to this plant to-night with one of two purposes in view.”

Hankinshaw started to protest, but Tom cut him short.

“Don’t add any more lies to those you’ve already told,” he said. “You may have had revenge in mind for what happened the other night down in the town. You may have thought that you’d be able to cripple the machinery here and put me to a lot of expense and trouble. That’s one possibility, and knowing you as I do I wouldn’t put it past you.

“On the other hand, you may have had it in mind to steal some invention I might be trying out here. You know that invention is my line, and you may have thought that I had discovered some improvement or new device to be used in oil digging that you could get hold of and turn to your profit. That would explain why you were so carefully handling and examining the tools here when we came upon you.

“One of these two things, perhaps both, was in your mind to-night when you stole in here like a thief. I don’t know which and I don’t care. But just let me tell you one thing, Hankinshaw. If I ever catch you hanging around this place again either by day or night, may heaven have mercy on you, for I won’t. There’ll be a guard here after this during every one of the twenty-four hours. He’ll be armed, and he’ll have his orders what to do to any vermin that may be trying to worm its way into this enclosure.

“Now, that’ll be about all. Stand up and get out of here and get out quick. Koku, you go down with him till he reaches the road. Don’t hurt him, but keep close behind him. Now, Hankinshaw, pick up that revolver of yours and go. And don’t forget a single word of what I’ve said to you, for I mean every syllable.”

The baffled miscreant got up, muttering things that he was careful to say under his breath. Koku, menacing as fate, stood hovering over him. The giant had not understood much of what had been said, but he knew that this man was his master’s enemy and nothing would have given him greater pleasure than to wring the rascal’s neck. Hankinshaw was fully conscious of this, and he sullenly pocketed the now useless revolver and moved toward the gate, with Koku stalking close behind him. As he passed Tom, he favored him with a glance that was malignity itself. Then he passed out into the darkness.

“Him bad man—so bad man,” grunted the giant, as he came back to Tom’s side.

“I reckon you are right, Koku,” answered the young inventor. “But we caught him red-handed, didn’t we?”

“Him like snake in the grass.”

“So he is.”

“Him do harm to Massa Tom. Must watch out.”

“Then you think he is a bad egg, do you?”

“Him worse than many bad eggs!”

“Well, maybe, Koku. We’ll see.”

Tom extinguished the lantern, hung it in its place, locked the gate carefully and returned to the office. It was now long past midnight, but he was too wrought up to have any desire to sleep. He sat with his elbows on the desk and his head in his hands, immersed in thought.

What had been Hankinshaw’s real motive? On reflection, Tom dismissed the idea that he had intended to cripple the machinery. Much more probable it seemed to him that the fellow had heard in some way that he was busy on some new invention, that the machinery had been rigged up for the purpose of testing it, and that he might make a fortune if he could steal the idea and have it patented before Tom himself should have time to do it.

But how could he have heard of it? Tom had been extremely careful to keep the matter in the circle of a few trusted friends. His father, Ned, Jackson and Mr. Damon were the only ones that knew of it. The first three would have been as silent as the grave concerning it. As for Mr. Damon, although he was impulsive and talkative, he was a keen business man and knew too well the importance of secrecy in a matter of this kind to speak of it to anybody, much less to a fellow like Hankinshaw, whom he disliked and distrusted.

There was but one conclusion. Hankinshaw had acted on a probability. He could not have been hanging around Shopton so long without having heard of the marvelous inventive genius of Tom, and he had jumped to the conclusion that this would have been turned in the direction of oil-well machinery while he was working to fulfill his contract. He had acted on the guess, and it was by the merest chance that he had been thwarted. If Koku had not happened to see that flash of light! Good old Koku!

One thing was certain. Hankinshaw, already an enemy, was now a deadly one. He would never forget or forgive the humiliation he had suffered that night. Tom must be on his guard.

Tom did not mention the matter of Hankinshaw’s behavior to his father the next day, because he did not want to worry him. He had also put Koku under a strict injunction not to speak of the events of the night. But to Ned, when he turned up at the office, he narrated the whole affair.

The latter was boiling over with indignation.

“It was a pity that you didn’t give him all that was coming to him,” he declared. “There isn’t a doubt but what you could have sent him to prison. Still, I suppose you were right in not giving the matter publicity. I tell you, Tom, we’re dealing with a shady crowd, and I wish we’d never taken the contract.”

“So do I,” agreed Tom. “And I’ll be heartily glad when the whole matter’s off our hands. Of course, this special thing was probably done by Hankinshaw without the knowledge of the others. He was playing a lone hand, and if he’d got hold of the invention he’d have got all the profit from it.”

“Maybe,” assented Ned. “But Thompson and Bragden, although more polished, are probably just as crooked at heart. It’s my opinion the whole gang are tarred with the same brush. All I want now is to see the last of them. When we’ve once delivered the last shipment and have got our money for it, I’ll feel like celebrating.”

“Well, we’ll only have to be patient for about two weeks more,” Tom consoled him. “Jackson agreed with me yesterday that it will take only that time to finish up the contract. By the way, how about that third check for five thousand? It’s due now, isn’t it?”

“Was due three days ago,” answered Ned. “Late, as usual. I’ve had to draw on them. Like pulling teeth to get anything out of them. We have to do our work twice over—once in actually doing it and the second time in getting our money for it. But we’ve got them on the hip now. They’ve paid so much that it will be more profitable for them now to pay the rest than to cheat us out of it.”

“There’s some silver lining to the cloud, anyway,” observed Tom more cheerfully. “If it hadn’t been for this contract I wouldn’t have been thinking about oil and wouldn’t have perfected this new idea of mine. We’ll forget all about this bother when the money comes rolling in from the patent rights. That is, if it does,” he added, with a return to his habitual caution.

“No modifications, you old gloom hound,” laughed Ned. “You gave yourself away that time. Own up, old boy, you know that you’ve got a good thing. Come now, don’t you?”

Tom grinned.

“On the level, Ned, I feel pretty sure of it,” he confessed. “Of course, ‘there’s many a slip between the cup and the lip,’ and I may be letting myself in for a disappointment. The next few days will tell. By day after to-morrow I’ll be all ready to put the new drill to a practical test. It won’t take long to know whether it’s going to work or not.”

The next two days were busy ones for Tom. He was, too, at high nervous tension, wondering whether his idea would “go over big” or fail. He had checked and re-checked on his figures, and could find no flaw in them. And figures did not lie. Still——

He saw nothing of Hankinshaw. Either the man had left town temporarily or he was keeping carefully under cover. Tom did not care which, as long as the rascal kept out of his way.

At last the momentous morning came when Tom was to try out his new drill. A few trusted workmen had been chosen to work the machinery. That was all they were concerned with, and they would be in no position to gauge the meaning of whatever results would be obtained. Jackson was there to help, and Ned and his father were also on hand.

The miniature well was started, and for a time nothing was heard but the creaking of the derrick and the chugging of the drill as it worked its way through the soil. Tom, of course, knew the ordinary rate of progress made in well digging with the usual type of drill. But by how much would he be able to beat it? Or would he beat it at all?

The morning passed with interest at fever heat. It seemed to Tom that he was making rapid progress. But the results of any one hour would not give him a sufficient basis to generalize from. Special circumstances might make the results small or great. The work would have to be spread over several hours before he could reach an average from which he could draw safe and sound conclusions.

At noon the men stopped for lunch, but Tom was too much excited to eat. He spent that time in studying the character of the soil through which the drill had been biting its way and the depth that it had reached.

The results astounded him. He thought he must have made a mistake in his calculations and went over them again. But no. The figures were correct. Was he dreaming?

His father, who had been looking over his shoulder, was equally startled.

“Why, Tom!” he exclaimed, “do you realize what that means? That’s three times as much as you could have got with the ordinary drill.”

“I know,” said Tom, in a voice that he tried to keep calm. “I thought I must have miscalculated. Do you see any error in the figures?”

“None at all,” was the answer. “They’re perfectly correct. But it seems almost beyond belief.”

“Well,” said Tom, “one swallow doesn’t make a summer, and one test doesn’t prove that others will be just like it. Perhaps the soil was lighter and easier to penetrate than it really seems. The real test will come when we strike rock.”

They struck rock that afternoon, and the way the drill ground and scrunched its way through it was music to Tom’s ears. It ate its way with surprising rapidity, which was the more remarkable because the specimens brought up showed it to be of a remarkably hard quality. Here again the same comparative gain was made over the ordinary rate of rock penetration.

Still Tom refused to be rushed off his feet, and the work went on for two days more, days of steadily decreasing doubt, days of steadily increasing jubilation.

At the end of the third day, Tom knew that beyond the peradventure of a doubt he had “struck it.” He would have been delighted if his new drill had proved to be able to do half as much again as the one commonly in use. He would have been astounded had it proved to be able to do twice as much.

But the result had far outrun his wildest expectations. The principle that he had embodied in his new drill had trebled its effectiveness. He had hit on something that was destined to revolutionize the oil industry.

Once more that inventive brain of Tom Swift’s would startle the world!