There was no question in the mind of Tom Swift but that the man he was running after was guilty of some wrong-doing. In the first place he was a stranger, and had no right inside the big fence that surrounded the Swift machine plant. Then, too, the very fact that he ran away was suspicious.

And this, coupled with the confusion on the part of Bower, and his proximity to the safe, made Tom fear that some of his plans had been stolen. These he was very anxious to recover if this strange man had them, and so he raced after him with all speed.

"Stop! Stop!" called Tom, but the on-racing stranger did not heed.

The cries of the young inventor soon attracted the attention of his men, and Jackson and some of the others came running from their various shops to give whatever aid was needed. But they were all too far away to give effective chase.

"Bower might have come with me if he had wanted to help," thought Tom. But a backward glance over his shoulder did not show that the new helper was engaging in the pursuit, and he could have started almost on the same terms as Tom himself.

The runaway, looking back to see how near the young inventor was to him, suddenly changed his course, and, noting this, Tom Swift thought:

"I've got him now! He'll be bogged if he runs that way," for the way led to a piece of swampy land that, after the recent rains, was a veritable bog which was dangerous for cattle at least; and more than one man had been caught there.

"He can't run across the swamp, that's sure," reflected Tom with some satisfaction. "I'll get him all right!"

But he wanted to capture the man, if possible, before he reached the bog, and, to this end, Tom increased his speed to such good end that presently, on the firm ground that bordered the swamp, Tom was almost within reaching distance of the stranger.

But the latter kept up running, and dodged and turned so that Tom could not lay hands on him. Suddenly, turning around a clump of trees the fleeing man headed straight for a veritable mud hole that lay directly in his path. It was part of the swamp--the most liquid part of the bog and a home of frogs and lizards.

Too late, the man, who was evidently unaware of the proximity of the swamp, saw his danger. His further flight was cut off by the mud hole, but it was too late to turn back. Tom Swift was at his heels now, and seeing that it was impossible to grab the man, Tom did the next best thing. He stuck out his foot and tripped him, and tripped him right on the edge of the mud hole, so that the man fell in with a big splash, the muddy water flying all around, some even over the young inventor.

For a moment the man disappeared completely beneath the surface, for the mud hole was rather deep just where Tom had thrown him. Then there was another violent agitation of the surface, and a very woebegone and muddy face was raised from the slough, followed by the rest of the figure of the man. Slowly he got to his feet, mud and water dripping from him. He cleared his face by rubbing his hands over it, not that it made his countenance clean, but it removed masses of mud from his eyes, nose, and mouth, so that he could see and speak, though his first operation was to gasp for breath.

"What--what are you doin'?" he demanded of Tom, and as the man opened his mouth to speak Tom was aware of a glitter, which disclosed the 'fact that the man had a large front tooth of gold.

"What am I doing?" repeated Tom. "I think it's up to you to answer that question, not me. What are you doing?"

"You--you tripped me into this mud hole!" declared the man.

"I did, yes; because you were trespassing on my property, and ran away instead of stopping when I told you to," went on Tom. "Who are you and what are you doing? What were you doing with Bower at my shop?"

"Nothin'! I wasn't doin' nothin'!"

"Well, we'll inquire into that. I want to see what you have in your pockets before I believe you. Come on out!"

"You haven't any right to go through my pockets!" blustered the stranger.

"Oh, haven't I? Well, I'm going to take the right. Jackson-- Koku--just see that he doesn't get away. We'll take him back and search him," and Tom motioned to his chief machinist and the giant, who had reached the scene, to take charge of the man. But Koku was sufficient for this purpose, and the mud-bespattered stranger seemed to shrink as he saw the big creature approach him. There was no question of running away after that.

"Bring him along," ordered Tom, and Koku, taking a tight grip on the man by the slack of his garments behind, walked him along toward the office, the mud and water splashing and oozing from his shoes at every step.

"Now you look here!" the gold-toothed man cried, as he was forced along, "you ain't got any right to detain me. I ain't done nothin'!" And each time he spoke the bright tooth in his mouth glittered in the sun.

"I don't know whether you've done anything or not," said Tom. "I'm going to take you back and see what you and Bower have to say. He may know something about this."

"If he does I don't believe he'll tell," said Jackson.

"Why not?" asked Tom, quickly.

"Because he's gone."

"Gone! Bower gone?"

"Yes," answered Jackson. "I saw him running out of the experiment shop as we raced along to help you. I didn't think, at the time, that he was doing more than go for aid, perhaps. But I see the game now."

"Oh, you mean--him?" and Tom pointed to the dripping figure.

"Yes," said Jackson in a low voice, as Koku went on ahead with his prisoner. "If, as you say, this man was in league with Bower, the latter has smelled a rat and skipped. He has run away, and I only hope he hasn't done any damage or got hold of any of your plans."

"We'll soon know about that," said Tom. "I wonder who is at the bottom of this?"

"Maybe those men you wouldn't work for," suggested the machinist.

"You mean Gale and Ware of the Universal Flying Machine Company?"

"Yes."

"Oh, I don't believe they'd stoop to any such measures as this- -sending spies around," replied Tom. "But I can't be too careful. We'll investigate."

The first result of the investigation was to disclose the fact that Bower was gone. He had taken his few possessions and left the Swift plant while Tom was racing after the stranger. A hasty examination of the safe did not reveal anything missing, as Tom's plans and papers were intact. But they showed evidences of having been looked over, for they were out of the regular order in which the young inventor kept them.

"I begin to see it," said Tom, musingly. "Bower must have managed to open the safe while I was gone, and he must have made a hasty copy of some of the drawings of the silent motor, and passed them out of the window to this gold-tooth man, who tried to make off with them. Did you find anything on him?" he asked, as one of the men who had been instructed to search the stranger came into the office just then.

"Not a thing, Mr. Swift! Not a thing!" was the answer. "We took off every bit of his clothes and wrapped him in a blanket. He's in the engine room getting dry now. But there isn't a thing in any of his pockets."

"But I saw him stuffing some papers in as he ran away from me," said Tom. "We must be sure about this. And don't let the fellow get away until I question him."

"Oh, he's safe enough," answered the man. "Koku is guarding him. He won't get away."

"Then I'll have a look at his clothes," decided Tom. "He may have a secret pocket."

But nothing like this was disclosed, and the most careful search did not reveal anything incriminating in the man's garments.

"He might have thrown away any papers Bower gave him," said Tom. "Maybe they're at the bottom of the mud hole! If they're there they're safe enough. But have a search made of the ground where this man ran."

This was done, but without result. Some of the workmen even dragged the mud hole without finding anything. Then Tom and his father had a talk with the stranger, who refused to give his name. The man was sullen and angry. He talked loudly about his innocence and of "having the law on" Tom for having tripped him into the mud.

"All right, if you want to make a complaint, go ahead," said the young inventor. "I'll make one against you for trespass. Why did you come on my grounds?"

"I was going to ask for work. I'm a. good machinist and I wanted a job."

"How did you get in? Who admitted you at the gate?"

"I--I jest walked in," said the man, but Tom knew this could not be true, as no strangers were admitted without a permit and none had been issued. The man denied knowing anything about Bower, but the latter's flight was evidence enough that something was wrong.

Not wishing to go to the trouble of having the man arrested merely as a trespasser, Tom let him go after his clothes had been dried on a boiler in one of the shops.

"Take him to the gate, and tell him if he comes back he'll get another dose of the same kind of medicine," ordered Tom to one of the guards at the plant, and when the latter had reported that this had been done, he added in an earnest tone:

"He went off talking to himself and saying he'd get even with you, Mr. Swift."

"All right," said Tom easily. "I'll be on the watch."

The young inventor made a thorough examination of his experiment shop and the test motor. No damage seemed to have been done, and Tom began to think he had been too quick for the conspirators, if such they were. His plans and drawings were intact, and though Bower might have given a copy to the stranger with the gold tooth, the latter did not take any away with him. That he had some papers he wished to conceal and escape with, seemed certain, but the splash into the mud hole had ended this.

No trace was found of Bower, and an effort Tom made to ascertain if the man was a spy in the employ of Gale and Ware came to naught. The machinist had come well recommended, and the firm where he was last employed had nothing but good to say of him.

"Well, it's a mystery," decided Tom. "However, I got out of it pretty well. Only if that gold-tooth individual shows up again he won't get off so easily.