Mr. Swift's eyes twinkled. "None of those," he replied as the boys stared, mystified. CHAPTER II THE MYSTERIOUS HITCHHIKER Tom and Bud were bursting with curiosity. Although the Swifts had been in radio contact with creatures from outer space for many months, this was the most exciting news yet! On one occasion, the unknown beings had moved a small asteroid--the phantom satellite Nestria--into orbit about the earth. Later they had sent strange samples of the animal life of their planet, aboard orbiting missiles, to be studied by the Swifts. They had also helped Tom, Bud, and Mr. Swift a number of times when their lives were at stake while on daring voyages beyond the earth. What was their latest intention? The telephone rang and Sandy went to answer it. "For Pete's sake, Dad," Tom pleaded, "don't keep us in suspense! Who or what is this visitor?" Mr. Swift smiled at the boys' baffled expressions. "The fact is that a message came through today that--" He was interrupted by Sandy who had come to the door. "The phone call's for you, Dad. Long distance from Washington." Bud groaned as Mr. Swift went off to take the call. "It's a conspiracy," Bud said. "Everyone's ganging up to keep us from finding out about that mysterious visitor!" Tom grinned. "We lasted through an earthquake this afternoon, pal," he said consolingly. "I guess we can last through a phone call." Inwardly Tom was as impatient as Bud about the exact nature of the message. Several months ago, the space creatures had sent their first communication in the form of mathematical symbols carved on a black missile which had landed on the grounds of Swift Enterprises. Tom and his father had decoded the symbols and beamed out a reply over a powerful radio transmitter. Later messages had been picked up by radio telescope and converted to appear as symbols on the oscilloscope screen. "Sandy must know what it's all about," Bud broke in. "She's the one who first mentioned the visitor." "Of course I know," Sandy said mysteriously. "So does Mother and so does Phyl. But don't think we're going to give it away!" she added teasingly. Tom and Bud cajoled the two girls and Mrs. Swift for further information. But Sandy and Phyl only shook their heads, obviously enjoying the situation. "At last we're getting back at them for the way they've neglected us!" Phyl said, her brown eyes sparkling with laughter. "Come on, Mother!" Tom said. "Be a sport. You tell us!" But Mrs. Swift too shook her head. "I'm sorry, Tom," she demurred gently, "but I think the girls are right. I'll say this much, though," she relented, "it will be the biggest challenge that Tom Swift Jr. and Sr. have ever faced!" "Whew!" Bud remarked as the two boys glanced at each other. "That must mean it's _plenty_ big news! It would have to be, skipper, to top all the other jobs you and your dad have taken on!"