to ice. A door to what? Where
did it lead? What would be on the other side of it? What could be on the
other side of a metal door on a world where it was doubtful that living
beings had ever existed at all?

There was a rasp in Nellon's earphones. And then Big Tim Austin's voice
followed it.

"Brad--I'm going in. This--why, this is the biggest find of the whole
expedition!"

"It might be dangerous," Nellon pointed out, before he could become
aware of the wealth of irony which lay behind the words. "We don't know
what sort of life--"

"But this door has been hidden under snow for the Lord only knows how
many years, Brad. Look where the crust had split here. It's thick,
thick. Nothing has gone in or out for a hell of a long time. If there
were beings, they're either gone or dead."

And, as if having satisfied himself on this last account, Big Tim
stepped directly up to the door. He was a tall man, yet he seemed
dwarfed beside it. And it was obviously very massive, for it was partly
open and the width of the edge revealed could not have been spanned by
the long, flexible metal fingers of their protecting gloves. The opening
was a mere crack, as if someone had once made it so for a cautious
glimpse of the world outside and never closed it again.

Big Tim placed his gloves against the projecting edge.

"Give me a hand, Brad. We'll see if we can open it further."

Together, they shoved. They drew upon ebbing reserves of strength, but
what energy they managed to summon they threw into a brief, terrific
effort to move the portal. But it did not move. Their combined strength
seemed pitifully small against the weight they sought to budge.

They were about to relax their efforts in despair when, suddenly,
transmitted from the metal of the door to that of their gloved hands,
they felt what seemed to be a coughing whir. The sound smoothed out,
deepened, and became a steady hum.

Startled, they leaped away. Their faces took on an intent, incredulous
expression.

The door was opening. Slowly, majestically, it was swinging wide.

* * * * *

No force that they could see was behind it. The door seemed to move of
its own volition. They stood as still as a pair of weird, metal statues,
watching. Every sense, keyed to its highest, was directed at the
widening gap.

At last all movement ceased, and the door hung wide. The humming note
which had accompanied its opening dwindled to a whisper an