"I think Koku is well able to handle any intruder," declared Tom confidently. "Besides, I think you're getting excited over nothing. You know Mr. Damon is inclined to make mountains out of molehills." [Illustration: "Koku Is Able to Handle Anyone."] "That's all very well," persisted his friend stubbornly, "but just suppose Mr. Damon is right in his suspicions? It'd be too late then to do anything about it." "Don't worry, old man. My Chest of Secrets will hold its contents secure against any burglar's attack. Now it's late. You'd better stay to dinner. Afterward, if you care to and have no other date, we can talk over some unfinished business." [Illustration: The Chest Would Guard the Secrets] "Thanks, Tom. I'll be glad to spend the evening with you." Locking up the laboratory, the two boys walked leisurely through the warm June twilight toward the big white house. Low in the sky hung the silvery crescent of the new moon, while almost overhead Mars glowed brightly. "There's our goal, Ned," murmured Tom, pointing to the red planet. "I feel sure that our meteorite came from that far-off world!" [Illustration: "There's Our Goal, Ned."] "Granting that it did come from another planet," objected Ned, "I don't get the reason why you're so sure it came from Mars. There are nine planets circling the sun, including the earth. Ruling out the sun, it seems to me that there is but one chance in eight that you are right." [Illustration: "Nine Planets Circle the Sun."] "If it were simply a matter of chance, there'd be a lot of weight behind your argument, Ned. But a lot of other factors enter the problem. I should say that the only planets where life as we know it might exist are Mars and Venus. The latter I ruled out, for astronomers have found that it is forever covered thickly with dense clouds. Thus the inhabitants, if any, must be ignorant of any world but their own." "What have people on the planets got to do with the question, anyhow?" asked Ned. "Huge chunks of metal break off of any heavenly body and go hurtling through space. The inhabitants don't throw them off!" [Illustration: Chunks of Metal Rushing Through Space] "But our meteor was no ordinary one as we have proved already," replied Tom. "I firmly believe that someone on another planet deliberately fired that missile into space, hoping it would reach this world. Since scientists agree that Mars probably is inhabited by a highly intelligent race, that planet is a reasonable guess." "Whew!" whistled Ned. "Such ideas are beyond me." [Illustration: "Someone on Another Planet Fired the Missile."] As he finished speaking, the boys reached the Swift residence. The young inventor's father had built the handsome white house many years before his son was born. Beyond were the several buildings where the inventions of Tom Swift and his father, Barton Swift, were manufactured.