*

He added vehemently, "Do you understand now why we should be suspicious
of this George Prince? He has a criminal record. He has a thorough
technical knowledge of radium ores. He associates with Martians of bad
reputation. A large Martian Company has recently developed a radium
engine to compete with our Earth motor. You know that? You know that
there is very little radium available on Mars, and our government will
not allow our own radium supply to be exported. That Martian Company
needs radium. It will do anything to get radium. What do you suppose it
would pay for a few tons of really rich radio-active ore--such as
Grantline may have found on the Moon?"

"But," I objected, "that is a reputable Martian company. It's backed by
the government of the Martian Union. The government of Mars would not
dare--"

"Of course not!" Captain Carter exclaimed sardonically. "Not openly! But
if Martian brigands had a supply of radium--I don't imagine where it
came from would make much difference. That Martian Company would buy
it."

Halsey added, "And George Prince, my agents inform me, seems to know
that Grantline is on the Moon. Put it all together, lads. Little sparks
show the hidden current.

"More than that: George Prince knows that we have arranged to have the
Planetara stop at the Moon and bring back Grantline's radium-ore. This
is your last voyage this year. You'll hear from Grantline this time,
we're convinced. He'll probably give you the signal as you pass the Moon
on your way out. Coming back, you'll stop at the Moon and transport
whatever radium-ore Grantline has ready. The Grantline Flyer is too
small for ore transportation."

* * * * *

Halsey's voice turned grimly sarcastic. "Doesn't it seem queer that
George Prince and a few of his Martian friends happen to be listed as
passengers for this voyage?"

In the silence that followed, Snap and I regarded each other. Halsey
added abruptly,

"We had George Prince typed that time we arrested him four years ago.
I'll show him to you."

He snapped open an alcove, and said to his waiting attendant, "Get me
the type of George Prince."

The disc in a moment came through the pneumatic. Halsey, smiling wryly,
adjusted it.

"A nice looking fellow. Nicely spoken. Though at the time we made this
he was somewhat annoyed, naturally. He is older now. Twenty-nine, to be
exact. Here he is."

The image glowed on the grids before us. His na