th long dark hair, Phyl
was the daughter of Tom Sr.'s old comrade-in-arms and lifelong chum
"Uncle Ned" Newton. Like Sandy, she was seventeen.

"You didn't think I'd miss this rare evening, did you, Tom?" she said,
laughing. "After all, it isn't often we see you two."

Sandy and Phyl liked to needle the boys about their infrequent dates,
due to Tom's and Bud's busy schedules.

Mrs. Swift, slender and sweet-faced, gave Tom a hug and greeted Bud
warmly. Over the delicious dinner, the conversation turned to the
mysterious thief missile.

"Who on earth could have fired it?" Sandy asked.

Tom shrugged. "No telling--yet. There's more than one unfriendly country
which would give a lot for the data picked up on our Jupiter shot."

"You aren't expecting more trouble, are you?" Phyl put in uneasily.

Tom passed the question off lightly in order not to alarm his mother and
the two girls. But inwardly he was none too sure of what his survey
expedition might encounter in trying to locate the lost probe missile.

Ever since his first adventure in his Flying Lab, the youthful inventor
had been involved in many daring exploits and thrilling situations. Time
and again, Tom had had to combat enemy spies and vicious plotters bent
on stealing the Swifts' scientific secrets.

His research projects had taken him far into outer space and into the
depths of the ocean. With his atomic earth blaster, Tom had probed under
the earth's crust at the South Pole, and in other adventures he had
faced danger in the jungles of Africa, New Guinea, and Yucatan. His
latest achievement, receiving the visitor from Planet X, had been to
construct a robot body for this mysterious brain energy from another
world. Now, Tom realized, he was on the brink of another adventure which
might hold unexpected dangers.

Early the next morning the majestic _Sky Queen_ was hoisted from its
underground hangar berth and hauled by tractor to its special runway.
This mammoth, atomic-powered airplane had been Tom's first major
invention. A three-deck craft, it was equipped with complete laboratory
facilities for research in any corner of the globe. Jet lifters in the
belly of the fuselage enabled the craft to take off vertically and also
to hover.

As Tom supervised the loading of the equipment, a foghorn voice boomed,
"'Mornin', buckaroos!"

The chunky figure of Chow Winkler came into view. Formerly a chuck-wagon
cook in Texas, Chow was now head chef on Tom's exped