lon's instincts
had revolted and the thing had remained undone.

But now the members of the expedition were preparing to return home to
Earth. Nellon knew that if Big Tim reached Earth alive the Laura he
remembered and wanted would be lost to him forever. If Big Tim was to
die, it would have to be done before the ship left, for once sealed
within its confines, the risks would be too overwhelmingly large.

It had been old Sigmund Ryska who had presented Nellon with what he had
realized was his final and only chance. Old Ryska had left several
pieces of valuable scientific equipment lying in a small hut which he
had set up for some experiments. He had remembered them at the last
moment. Someone had to fetch them before leaving, and Big Tim Austin had
volunteered. Nellon, because of the purpose which motivated him, had
gone along.

He had made up his mind at last. This time he would allow no scruples to
stay his hand. This time Big Tim would die.

* * * * *

They had reached Tower Point. Nellon's breathing had quickened, and a
fine perspiration had broken out upon his face. Fine lines were etched
around his eyes and mouth.

Nellon and Austin stood side by side a moment upon the summit which was
crowned by the great pinnacle of Tower Point. Down below glittered the
surface of the frozen lake. White and desolate, the frozen wastes of
Titan tumbled and leaped on every side. Snow swirled about them, whipped
into angry life by the gale.

Austin turned.

"Well, down we go. Watch it, guy." For a second his eyes locked with
Nellon's. A frown of perplexity and concern narrowed them.

"Brad--anything wrong? You don't look right, somehow."

Nellon felt himself go icy cold. Words of hoarse denial tumbled to his
lips.

"No--it's nothing. I--I'm all right."

But Big Tim was not assured.

"Listen, Brad, Ryska's hut isn't much further, now. You'd better wait
here, and I'll go on ahead and get the stuff. It's hard and dangerous
going, and if you aren't well--"

"I tell you I'm all right!" Nellon blurted. He was hot now with a
feverish warmth that made the perspiration which covered his body feel
clammily cold. The old fear of murder was gone. Nellon knew only a
burning desire to get the thing done, a wild alarm that his opportunity
would vanish before he got the chance.

Big Tim shrugged.

"Come on, then. But watch it, guy, and sing out if you need me." With a
last troubled glance at Nel