rolling ceased. The others drew back;
he turned down another tunnel.

They stopped at the cave beyond the one where he had found the
robot-girl. It was sealed by a locked door, one of the airlock-doors
from that space vessel, firmly cemented into the natural opening of the
cave.

Nat bent forward, listening, his helmeted head pressed against the
door. No sound. He was suddenly aware of the dead silence that pressed
in on him from all sides now that the globes no longer sang and his
"squeaker" had been turned off. The powerful energy of his heat-beam
sputtered as it melted the lock into incandescent droplets which
sizzled as they trickled down the cold metal of the door. The greasy,
quartz-like material at the side of the door glowed in the heat from
his rod, but no visible effect upon it could be seen. What was that
material? He knew, yes, he knew--but he could not place a mental finger
on it.

He thrust the shoulder of his good arm against the heavy door, swung it
inwards, stepped inside. The light of his torch pierced the silence,
picked out a human skeleton in one corner. He hurried toward it--no, it
was not entirely a skeleton as yet. The flesh and bone had been eaten
away from the lower part of the body to halfway up the hips, as though
from some strong acid. The rest of the large, sturdy frame lay sunken
under the remains of a spacesuit which was tied clumsily around the
middle to retain all the air possible in the upper half of it.
Evidently some acid had eaten away the lower half of the man's body
after he had suffocated. The face was that of a Norwegian.

By one outstretched hand a small notebook lay open with the leather back
upward. The corners of several pages were turned under carelessly--Nat
swung the torch around the room. It was bare. The notebook--quickly he
picked it up. The page on which the writing began was dated May 10,
2040. About two months ago.

"Helmar Swenson. My daughter, Helena, aged nineteen, and I were lured
into the maw of this hellish monster by a robot calling for help in our
television screen. This thing, known to man as Asteroid Moira, is, in
actuality, one of the gigantic mineral creatures which inhabited a
planet before it exploded, forming the asteroids. Somehow it survived
the catastrophe, and, forming a hard, crustaceous shell about itself,
has continued to live here in space as an asteroid.

"It is apparently highly intelligent and has acquired an appetite for
human fles