Rightly arguing that no one who had a right to be there would try to enter in this manner, Tom Swift decided to find out who was opening the door, and in such a manner as to capture the intruder if possible. Accordingly, he made a sign to Ned to keep quiet and then began creeping toward the door in as stealthy a manner as it was being opened, which was a fraction of an inch at a time.
Ned, seeing his chum's intention, followed him, and the two were close to the door when, unfortunately, Tom stumbled over a piece of wood left by one of the workman. The noise, though slight, was enough to alarm the person on the other side of the door. It was at once pulled shut and footsteps could be heard in hasty retreat outside.
"After him!" yelled Tom, caution now being useless, and he and Ned made a dart for the opening. They swung back the door, but it had stuck a little, and the two youths were just in time to see a crouching, running figure some distance away.
"Catch him!" cried Ned.
It was easier said than done. When Tom and Ned reached the place where they had caught a glimpse of the running figure there was no sign of the fugitive. Though an alarm was at once raised and a search made, no stranger was discovered on the place.
"Well, what do you make of it?" asked Tom, when the two had returned to where the House on Wheels stood.
"Hanged if I know what to make of it," Ned replied. "Whoever it was thought no one was in here, and they thought they could either steal your House or else damage it."
"It would be hard to steal it," replied Tom. "But it wouldn't take much to wreck it. Looks as if some of the old gangs were after me, or else some new one."
"I'm inclined to the latter theory," said Ned. "And the newest one who would logically have it in for you is Cunningham. Isn't that the case?"
"I suppose so. Yet I can't understand a man of his business ability—and I must admit he is shrewd—being foolish enough to risk an attack such as this might have been."