Curt felt the airship going out of control as he passed over a rock spattered stretch of sand. Automatically he looked for a smooth place to land and steered the bucking ship for it. The jolt of the landing triggered the ejector seat and in a second he was hurtling through the air away from the explosion of the damaged vehicle. Just before he blacked out, he thought—almost calmly—"a good hundred and fifty miles from the colony."

When he regained consciousness, night was passing and the first of the three suns was peeking over the horizon. Curt lay still for a while, afraid to find out what might be wrong with him. And the rescue ship could take anything from an hour to a week to find him. He moved his head to discover if there might be anything left of his ship; he saw nothing but pieces.

"Well," he said aloud, "so much for that." He reached back gingerly and undid the seat straps. Carefully, he sat up and began to ease his weight onto his feet. A sharp twinge of pain in his knee dropped him back to a sitting position. He probed at the knee but found no broken bones.

"Well," he said again, quietly. The colony leaders had had very little to offer in the way of survival. Rule number 1: Mark the crash site and your direction of travel. Number 2: Get into shade before the combined heat of the three suns boils your blood. Number 3: Carry your pistol for protection against liquid scorpions, and always save the last pellet for yourself.

Curt glanced about nervously at the thought of the liquid scorpions—the one form of animal life the colonist had found on this mineral-rich planet. Liquid scorpions were enormous masses of clear, jellyish liquid that oozed forward across the rock and sand with remarkable speed. A liquid scorpion changed shape constantly, its mass shooting out legs wherever they were needed. Only the eyes, fixed in a bulge over the center of its mass, and the almost-solid, curved stinger that arched over its back remained the same.

The first landing party had stood transfixed while one of the crew was attacked and absorbed before their eyes. Clear, the scorpion had been almost invisible to them until it flowed about the navigator's legs and paralyzed him with the swaying stinger. When his frantic struggles had ceased, the creature flowed over his body and absorbed it. As the party watched, the clearness slowly became a thin, dark red, and the body could no longer be seen.

Avengers had poured out of the ship after the giant scorpion, which reared back, tripling its height and halving its width. At the apex, the two protruding eyes bulged at them and the stinger swayed back and forth, reaching out and retreating. Explosive pellets fired into its flesh were absorbed with a slurping sound. The captain in the end, had knelt and taken careful aim at the right eye, behind which was the only unreddened sector of the mass. When the right eye disappeared, the clear area spurted out of the hole and drained over the jelly-like surface. Slowly, silently, the first of the liquid scorpions died.

Curt counted the pellets in his belt—an even hundred. Enough ... if he managed to keep out of sight and had good enough aim. He surveyed the surrounding countryside. Farther along the valley were shaded caves where he could find protection once he had marked his course.

If he could walk that far.

Xen came sluggishly awake, feeling the warmth penetrate his mass. The time of heat had come again, the time to search for what would halt the hunger that ached through every inch of him.

Slowly, his cold-stiffened mass flowed forward from its hiding place in the warmth-holding sand. The heat melted the stiffness out of him and he began to slide across the sand, his alert senses functioning again. Sense of touch led him across rocks and over ridges easily. The touchy sense of vibration waited apprehensively for movement that would shake the ground. And the third sense, the one that could be called only "sense" or "sense of knowing," functioned as always without his understanding. Today, this third sense told Xen, was different from other days.

Extra-cautious, Xen oozed over rocky barriers in the direction that his "sense" told him held food. Once he felt a slight tremor, and in terror flooded out over the rock into thin, transparent nothing. He waited several degrees of heat, but no further movement touched the sensitive receivers in his mass.

A falling rock, he decided, collecting himself and starting forward again. He slithered down rocky walls, pouring almost like water when the drop was long and drawing together at the bottom. When his feeling of touch warned him of the shade whose coolness might solidify him and leave him helpless in the open, he drew hurriedly away and changed direction.

Finally, he reached an open spot that was likely to contain food. His mass ached for something to consume, but he flooded himself thin again and waited, feeling. There was no vibration through the surface, nor did his "sense" tell him of anything other than the possibility of nourishment. Xen hesitated only a degree of heat before bubbling excitedly into the open space.

Touch found him something edible almost immediately—he flowed around and over it, absorbing it hungrily. His mass dissolved it almost immediately and ached for more. He slid thin, reaching out in every direction until contact was made, then absorbing the food instantly and moving on.

Curt, lying in meager shade that would be gone in half an hour when the third and largest sun rose, first saw the movement when it was on the rocks. His already frayed nerves gave a frightened leap. He lay perfectly still. Where he had seen the movement on the rocky shelf there was now nothing.

The nothing moved forward.

Curt shivered. He was certain he was seeing nothing, and yet his eyes were trying to tell him there was movement. When it reached the flat place and flowed swiftly forward, he realized that it was a liquid animal and was suddenly pointedly conscious of the weight of the pistol against his hip.

He watched carefully for the eyes and the stinger, but saw none. That frightened him. If he could not find the brain, he had no mark to shoot at. As he watched, the liquid creature flowed against one of the hardy, sun-browned plants and jerked in reaction. Instantly, it flowed over the plant and absorbed it. The liquid turned momentarily a thin brownish green and then cleared again.

Curt watched it with narrowed eyes. It was just possible that this creature ate only plant life. The colonists had realized that the liquid scorpions had fed upon something else before they arrived, but no one had been able to discover what that something was.

Xen was in the process of absorbing a plant when the vibration sense alerted him. Terror shot through him and he spread thinly across thirty feet of ground and lay motionless, his "sense" telling him frantically that a Sting was hunting nearby.

He lay for many degrees of heat, waiting. Sense of vibration and knowing both told him that the Sting was approaching, but uncertainly, searching. Then both senses reacted startledly to a new danger on the other side. New movement! A new feeling that his "sense" could not understand.

The Sting was approaching at an angle that would inevitably bring it in contact with Xen. Absorption was the penalty for being caught. Xen was resigned to death, for he could not possibly escape the Sting. And now there was this new sensation on the other side of him. Whatever it was, he had no idea; but likely it was as voracious as the Sting.

Now the new thing vibrated jerkily around him and stopped between him and the Sting. The vibrations from the eager Sting accelerated rapidly, eagerly, as it flowed over the ground. Then, for no reason except that the new creature had moved slightly, the Sting recoiled. The jerks were plainly recorded through the earth to Xen; and as he felt the heavy jar, his "sense" told him that the danger from the Sting was past. The Sting was dead.

Xen drew himself together and considered that.

The new thing vibrated jerkily the place from which Xen had first felt it move. It must be solid as the rocks to move so jerkily, Xen thought. The Sting-killer drew itself back under the enormous rock and ceased to move.

Curiosity drew Xen forward, fear dragged him back. He spread thin and drew together with uncertainty. At last, he oozed forward carefully until he reached the rock. The Sting-killer was pressed back under the rock, where touch told Xen a tiny amount of the cold-carrying shade remained. Xen puzzled at that. Why should this creature hide from the life-giving suns?

He reached out and absorbed a plant thoughtfully. This thing was different from the liquid structures he had always known. If it was solid where they were liquid, perhaps then it was also opposite in its needs. Maybe this Sting-killer needed cold instead of heat.

While Xen was considering this difficult thought, the Sting-killer began to move again.

Curt gasped. The shade was gone. The third sun was reaching long rays under the rock to sear his already-burned flesh. He had to find more shade.

Movements were very painful. His lips were cracking and his face had blackened. The injured knee had swollen inside the protective suit; it throbbed and ached. Dazedly, he pulled himself to his feet.

On the rock beside him, spread an inch thick, was the almost-invisible creature he had been forced to circle in order to stop the liquid scorpion. He wondered tiredly if it was dangerous. It lay completely motionless, just as it had when the liquid scorpion had approached. So it was probably more afraid of him than he was of it. He turned away. There appeared to be shade down the valley—perhaps a mile, perhaps three. Too much for him, he knew, but he set out, feeling the sun beat cruelly at him, crying out when the pain in his knee forced him to catch his balance against the sun-heated rock.

He knew without turning that the liquid creature was following him, stopping when he stopped, starting when he started. When he knew he could go no farther and felt his knee give weakly to his weight, he saw it ooze forward and began to flow over his legs. He tried to reach his pistol, but it seemed so far away.

Xen, following the Sting-killer curiously, put together all that he had learned. This creature was different from himself. It needed shade. It had killed his enemy, which was possibly also its own enemy. Now it was trying to reach the shade, but its progress grew steadily slower.

He considered that progress. The only thing he could liken it to was one of his own kind, caught out in the time of cold, trying to reach the heat-retaining sands, slowly congealing into a solid mass and dying. This, then, was the reverse process. Perhaps the Sting-killer would become liquid after a certain degree of heat.

Xen's sense of knowing warned him gently about too much wandering in the open, where countless Stings could be hiding. He drew back, unwilling to stop following this interesting creature. The Sting-killer vibrated the ground and lay still suddenly. Xen waited for a "sense" of death but none came. This might be for the new thing a stage similar to that when one of Xen's own kind became unable to move from the cold, but still lived and feared.

Caught between his own fear and a very strange sensation that he could not interpret, Xen waited a degree of heat. Then he oozed forward and spread himself over the still shape, until it floated within him. When he flowed over one part, the thing struggled pitiably. Xen drew back startedly and the movement ceased. Carefully, he retraced his course, leaving the part free. This time there was no struggling.

Spurred by fear of Stings, Xen began to flow across the land, letting his "Sense" guide him to the coldness. He slithered up slopes, poured over steep drops, always collecting himself in time to catch his burden.

He found a place that would stay cold until the next time of heat and halted in front of it, his anxiety evident in the way he spread and collected himself, back and forth. At last he inched forward, feeling the agony of the cold bite into every cell. Bunching himself behind the Sting-killer, he made it flow along him until it broke free and lay upon the shaded rock. Xen drew back as hurriedly as his already-sluggish mass would allow. He spread thin across the earth and let the heat liquefy his body again....

It was when the time of cold was only a few degrees away that Xen felt the heavy vibration which nearly made him dissolve with fear. It lasted for a few degrees and then weakened and made only a small tremor. Now many smaller vibrations reached him, like many creatures moving about. The tremors spread out, moving slowly toward the rocky valley.

Xen lay still trying to identify the vibrations. They were not those of Stings. As they approached, he recognized them as resembling in great numbers the creature he had put upon the rock.

Curt imagined he heard voices, an incoherent babble of them. He struggled to sit up, but there was an incredible weight on his chest.

"Lie still," a voice said clearly, and his mind echoed, "Still ... still ... still...."

He struggled again. "Liquid," he croaked painfully, "liquid animal ... liquid...." The weight was still there. He heard one last voice say, "Poor guy, he must have run into scorpions."

Then he was lifted and it seemed as though the lifting would never cease.

Xen waited until the small tremor was gone and the great vibration had roared and disappeared. He knew by the sense of emptiness that the Sting-killer had gone back to his own kind. For a moment he felt very alone, though he knew the sand was full of Xens.

Slowly, he drew himself together. For the time of cold was but a few degrees away, and he must seek the warm sands.