"Maybe not, but perhaps the crazy machinist will," suggested Mark. "I'll make some inquiries to-morrow, and see if the Martians know anything of him," promised Mr. Henderson. But if the Martians knew anything of the insane man, they would not tell. When the adventurers made cautious inquiries on the morrow, they were only met with vacant stares from the big eyes. The boys and their friends made several excursions about Martopolis in the next week, and even traveled in the big sleds to distant cities, which they found much the same as the one they were in. They saw no signs of the crazy machinist, and began to believe that he had disappeared for good. They were making progress in the Martian language, and could converse with the people. No longer did the Martians cause the travelers to move about by the thought force, and our friends were allowed to go here and there as they pleased. They found traveling exceedingly easy, as their bodies were so light. They had again taken up their residence in the house in the city, paying occasional visits to the projectile, which remained on the soft sand where it had landed, but tilted upward, ready for a flight. One afternoon Jack and Mark, who had been out taking a walk, came back rather hurriedly. They found Professor Henderson and Mr. Roumann doing some scientific work, while Washington and Andy were discussing the many strange things on Mars. "Professor," said Jack, "I think something is up." "What do you mean?" "Well, there's something unusual going on. The Martians are acting very queerly. There's a big meeting in the glass palace, and when we tried to go in we were stopped. Crowds in the street kept following us, and they haven't done that since we first landed." "Yes," added Mark, "and I think I saw that same man who watched us taking the Cardite with a lot of other officers, following us, too. And, besides, no persons here seem as friendly as they used to. Did they, Jack?" "No, indeed. I think they have discovered that we have taken some of the red stuff, and they don't like it." Professor Henderson and Mr. Roumann looked grave. If this was the case, it might mean serious trouble for them all. "But they're a long while finding out that we took the stuff," said Andy, who listened intently to what the boys said. "Maybe they knew it all the while," suggested Jack; "but they are so interested in scientific matters that they didn't want to take any action on it until now." "Well," remarked Mr. Roumann, "whatever it is, I think we will be safer in the projectile. Come, we will all go out there and spend the night. We can defend ourselves in case anything happens, though I don't believe it will." They started at once, and there was a feeling of security when they had clamped fast the great steel doors in the side of the Annihilator.