Jack hesitated a moment, listened to detect any possible ticking of some hidden clock mechanism, and then, as no sound came from the object, he picked it up. Rapidly tearing off the paper, he disclosed a harmless, red brick. "Some one wanted to scare us," remarked Andy. "There's a paper wrapped around the brick--a white paper," said Professor Henderson. "So there is," spoke Jack as he removed it. "There's writing on it, too." He held it up to the light. "It's a message," he went on, "and not a very pleasant one, either." "Who's it from?" asked Mr. Roumann. "It's signed 'The Crazy Machinist', Jack, and this is what it says:" "Beware, I am still after you! I will yet blow you sky-high!" "He threw that in through the window!" cried Mark. "He must be outside here. Let's see if we can't catch him." "That's right," added Jack. "Andy! Washington! Come on!" The boys, followed by the hunter and the man, hurried from the house. CHAPTER XIV OFF FOR MARS It was dark outside, and coming from the lighted room, the searchers at first could discern nothing. Then, as their eyes became accustomed to the gloom, they could make out objects with greater distinctness. A movement in a tree, just outside the broken window, attracted the attention of Andy. "Here's something!" he cried. He raised his gun, which he had caught up as he rushed from the house, and fired high enough in the air, so as not to hurt whoever was in hiding. The flash of the weapon showed a man in the act of sliding down the trunk. "Catch him!" cried Jack. They all made a rush for the tree, but the flash of Andy's gun, while it revealed the man to them, also had the effect of momentarily blinding the men and boys. For an instant they could see nothing, and when the effect of the flash passed away the man was not in sight in the semi-gloom. They could hear him running through the underbrush outside of the garden, however, and took after him. But the crazy machinist, if indeed it was he, got away, and after a vain search through the garden and about the machine shed, they all returned to the house, Mr. Roumann and the professor having joined in the hunt. "What do you suppose he did it for?" asked Mark, when they were again gathered in the dining-room, examining the strange message. "He wanted to scare us," suggested Jack. "No, I really think he means to do us an injury," said Mr. Roumann. "He has some fancied grievance against us, or he is being used as a tool by Zeb Forker. Perhaps the man who stole the plates was with him, and he hoped to get some more during the confusion. I think we had better take a look at the machine shop." They acted on this suggestion, but an examination there showed that nothing had been disturbed. No one had been in the place. "I'm going to sleep here to-night," said German scientist. "I'm not going to take chances at the last moment. I'll stay here."