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!"

Conquering outer space, probing the ocean's secrets, drilling to the
earth's core--these were only a few of Tom Swift's many exciting
exploits.

In his first adventure, Tom, in his Flying Lab, had gone to South
America to fend off a gang of rebels seeking a valuable radioactive ore
deposit. In his most recent challenge, Tom had defied the threats of
Oriental killers determined to ferret out the secret of the Swifts'
latest space research.

As the two boys silently recalled the exciting events of the past
months, Mr. Swift returned to the living room.

Tom and Bud leaned forward in their chairs. "Well, boys," Mr. Swift
said, "as I started to tell you, the space receiver picked up a message
today from our unknown planetary friends. The message informed us that
they are sending a visitor to earth--a visitor consisting of _pure