“A great plant—a wonderful plant!” mused Tom. It gave him a certain sense of pleasure to dwell thus in introspection on the accomplishments of his father and himself. And it buoyed him up for the work in prospect—for Tom Swift had a great plan in mind, a plan so great and daring that, as yet, he had said but little of it even to his father or to Ned Newton, his old chum who was now an officer of the concern. “But it can be done! I know it can be done!” declared Tom. “And I’m going to do it! I’m going to——” In his mental energy he had unconsciously spoken the last words in a low voice, but the sight of something just ahead of him in the gathering darkness caused him to break off abruptly and halt suddenly. Concentrating his gaze, Tom Swift looked eagerly at a clump of bushes. “It’s a man,” murmured Tom Swift. “A man, sure enough, and it isn’t one of our workers, either. None of them would sneak around as he is doing.” For that described exactly the movements of the stranger of whom Tom had caught sight in the darkness as he approached the big fence which surrounded his plant. “What’s he up to?” mused Tom. “No good, that’s sure. He wouldn’t sneak along like that if he were on the level.” Through Tom’s mind flashed remembrances of times when attempts had been made by enemies of himself and his father to fire the plant. To prevent this, and to keep strangers away, a high fence had been erected around the buildings. This fence was protected by wires on the plan of a burglar alarm, so that, no matter at what point the barrier was climbed, a bell would ring in the main office and on an indicator would appear a number to show at what part of the fence an attempt was being made to scale it. An effort to break down the barrier, or burrow beneath it, would also sound the alarm in like manner. So Tom had no fear that the sneaking stranger, crouching along in the darkness, could get into the midst of the buildings without notice being given. “But what’s his game?” thought Tom. Almost at the instant he asked himself this question he saw the man crawl behind a clump of bushes. In the natural course of events the man should have appeared on the other side of the clump. But he did nothing of the sort. “He may be hiding there,” mused Tom. “Perhaps waiting for a confederate. I’ll just have a closer look at this!” He advanced boldly toward the bushes. There was nothing between him and the shrubbery, and it was still light enough to see fairly well. Besides, Tom had extraordinarily good eyes. His astonishment can be imagined when, on reaching the bush off which he had not taken his gaze and behind which he had seen the crawling man disappear he found—no one! “That’s the queerest thing I’ve seen yet!” exclaimed Tom, rubbing his organs of vision.