pain and its 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 flesh. The singing spheres act as its sensory organs, separated from the body and given locomotion. It uses these to lure victims into its stomach in the first cave. I escaped its lure at first because of the 'squeaker' I carried with me. We set up these two doors as a protection from the beast while we stayed here to examine it. But the monster got me when I fell and the 'squeaker' was broken. My daughter rescued me after the acid of the pool had begun eating away my flesh.

"My Helena is locked in the room opposite this one. She has food and water to last until July 8th. Oxygen seeps in there somehow—the beast wants to keep her alive until it can get her out of the room to devour her."

Here the writing became more cramped and difficult to read.

"I have put the key in my mouth to prevent the spheres from opening the door should they force their way into this room. Some one must come to save my Helena. I can't breathe—"

The writing ended in a long scrawl angling off the page. The pencil lay some distance from the body.

July 8th! But that had been almost a week ago!

He unscrewed the man's helmet, tried to pry the jaws open. They would not move; the airless void surrounding the tiny planetoid had frozen the body until now it was as solid as the quartz cave-walls. There was but one thing to do: the other door must be melted down.

He leaped halfway across the room toward the door in the opposite wall. Could it be possible that he was in time?