the municipal spaceport.

The boys didn't talk much on the way out, each wondering why Captain
Strong was recalled on such short notice, and why he had left without
saying good-by to them. They knew they would see him in a few days when
the processing of the Luna City applicants was over and they would
return to Space Academy, but the relationship between the cadets and the
Solar Guard captain had developed into a deeper association than just a
cadet crew and officer supervisor. They were friends--spacemates! And
the boys sensed trouble ahead when they arrived at the Luna City
spaceport. They stood in the shadow of the _Polaris_ and stared into the
sky to watch the globe that was Earth revolve in the depths of space.
The outline of the Western Hemisphere, flanked by the shimmering
Atlantic and Pacific oceans, could be seen clearly. It was a
breath-taking view of a world that had given birth to all the men who
now took the travel from one world to another for granted.

"Gosh," said Tom, staring at the magnificent sight. "I see the Earth
like that every time we blast off from Luna. I should be used to it by
now, but--" he stopped suddenly and sighed.

"I know what you mean, Tom," said Astro. "It's the same with me. Gets me
right here," and he put his hand to his heart.

"You don't know your anatomy yet, pal," drawled Roger. "Move your hand
down a couple of inches. Things only get you in the stomach."

"Oh, is that a fact?" growled the big Venusian. Suddenly, without any
apparent effort, he picked up the blond cadet and held him high in the
air. "Which way shall I drop him, Tom? On his head or the seat of his
pants? Seems to me it won't make much difference."

Tom laughed at the spectacle of Roger flailing the air helplessly, then
suddenly stopped and grabbed Astro by the arm. "Wait, Astro," he called.
"Look! There's someone in the ship!"

"What?" cried Astro, dropping Roger and turning to the _Polaris_. The
three cadets saw light gleaming from the control-deck viewport.

"Well, I'll be a space monkey!" exclaimed Roger. "Who could it be?"

"I don't know," replied Tom. "Governor Hardy is at the Luna City Hotel,
and Captain Strong is the only one besides us who has the light key to
open the air lock!"

"Well, what're we waiting for!" said Roger. "Let's find out what's going
on!"

The three cadets climbed into the ship and raced up the companionway to
the control deck.

"No one here," announced Roger as he stepp