alone at night, and
the sudden flash on the field a few days before when they had won the
mercuryball game. Was there some reason behind his companion's strange
actions? In vain, Tom racked his brain to find the answer. There had to
be some explanation. Yet what could it possibly be? He tossed and turned
and worried and finally--comfortable as the monorail car was--he fell
asleep from sheer exhaustion.

* * * * *

Atom City! Built of the clear crystal mined so cheaply on Titan, moon of
Saturn, Atom City had risen from a barren North American wasteland to
become a show place of the universe. Here was the center of all space
communications--a proud city of giant crystal buildings. Here had been
developed the first slidewalks, air cars, three-dimensional stereos and
hundreds of other ideas for better living.

And here at Atom City was the seat of the great Solar Alliance, housed
in a structure which covered a quarter of a mile at its base and which
towered three thousand noble feet into the sky.

The three cadets stepped out of the monorail and walked across the
platform to a waiting air car--jet-powered, shaped like a teardrop and
with a clear crystal top.

"We want the best hotel in town," said Astro grandly to the driver.

"And get this speed bug outa here in a hurry," Roger told him. "There's
a lot we want to do."

The driver couldn't help smiling at the three cadets so obviously
enjoying their first leave.

"We've got three top hotels," he said. "One's as good as the other.
They're the Earth, the Mars and the Venus."

"The Earth," voted Tom.

"The Mars," shouted Roger.

"The _Venus_!" roared Astro.

"All right," said the driver with a laugh, "make up your minds."

"Which of 'em is nearest the center of the city?" Tom asked.

"The Mars."

"Then blast off for Mars!" ordered Tom, and the air car shot away from
the station and moved up into the stream of expressway traffic fifty
feet above the ground.

As the little car sped along the broad avenue, Tom remembered how often,
as a boy, he'd envied the Space Cadets who'd come to his home town of
New Chicago on leave. Now here _he_ was--in uniform, with a three-day
pass, and all of Atom City to enjoy it in.

A few minutes later the air car stopped in front of the Mars Hotel. The
cadets saw the entrance loom before them--a huge opening, with ornate
glass and crystal in many different colors.

They walked across the high-c