"What in the name o' tarnation did he want with that?" demanded Captain Britten as the giant stone was lowered cautiously to the deck. Weighing many tons, it had tilted the barge far over to one side as the powerful derrick drew it up. "It looks like some old rock a man might pick up 'most any place." "Oh, Tom Swift usually has a good reason for everything he does," smiled Ned noncommittally. "I'm no scientist, but he is, so perhaps he wants to experiment with this stone from another planet." [Illustration: The Powerful Derrick Drew It Up] At last the three divers reached the surface and were hauled rapidly up to the deck of the barge. All of them appeared exhausted, but Tom's eyes expressed the greatest satisfaction when he saw the meteorite safely aboard. At his request the tug was put under way and the "Betsy B." started back to her home port in Key West. During the trip Tom managed to cut from the meteorite a fifty-pound chunk. [Illustration: Tom Cut off a Large Chunk] "I'm very eager to see if this stone contains more X," he explained to Ned, "so I'm planning to fly straight home with this sample to analyze it. I want you to put the rest of the meteorite on a fast freight train and travel north with it." The sun was setting when the dock at Key West was reached. Tom waited no longer than was necessary to take on a supply of gasoline for the "Winged Arrow." He paid Captain Britten a generous fee and added a bonus for the divers who had helped him. Then with a hasty good-bye the excited young inventor roared off in the gathering darkness toward his distant home. [Illustration: He Paid Captain Britten] After an uneventful flight he reached Shopton at about half-past one the following morning. The wheels of the plane had barely stopped turning when the tall figure of Koku came rushing out of the shadows of the hangar to greet his master. [Illustration: Koku Came Rushing Out] "You're right on the job!" exclaimed Tom, climbing stiffly from the cabin. "How is everything?" "All thing good!" declared the giant, grinning to see the young inventor back. "Catchum skystone?" "We caught it, all right. You might tote this sample of it over to the lab." Tom handed his servant the segment he had chiseled from the main mass. "Master knows 'bout secret cave under lab'tory?" questioned the giant as the two walked across the field in the moonlight. [Illustration: "Tote This Sample to the Lab."] "Cave? Oh, you mean the vault?" asked Tom, who had been thinking of other matters. "Night you go 'way in sky-bird, Koku watch. Koku hear bell go ting-ting-ting!" Suddenly Tom was paying strict attention. "Great Scott! D'you mean to say someone broke into my Chest of Secrets? Tell me about it quickly!" [Illustration: Tom Paid Strict Attention] CHAPTER X SUCCESS "Me tell!" said Koku. "Hear bell, know bad mans hide in cave. I creep up an' watch!" His dramatic pause might have seemed funny at any other time but Tom was badly worried.