Agee staggered back from the panel and collapsed. Victor was already at the door to the cargo hold, trying to hammer it down with his fists. Barnett covered his mouth with one hand and rushed to the panel. He fumbled blindly for the switch, feeling the ship revolve giddily around him.

Victor fell to the deck, still beating feebly at the door.

Barnett jabbed blindly at the panel.

Instantly the generators stopped. Then Barnett felt a cold breeze on his face. He wiped his streaming eyes and looked up.

A lucky stab had closed the ceiling vents, cutting off the yellow gas. He had accidentally opened the locks, and the gas in the ship was being replaced by the cold night air of the planet. Soon the atmosphere was breathable.

Victor climbed shakily to his feet, but Agee didn't move. Barnett gave the old pilot artificial respiration, cursing softly as he did. Agee's eyelids finally fluttered and his chest began to rise and fall. A few minutes later, he sat up and shook his head.

"What was that stuff?" Victor asked.

"I'm afraid," Barnett said, "that our alien friend considered it a breathable atmosphere."

Agee shook his head. "Can't be, Captain. He was here on an oxygen world, walking around with no helmet —"

"Air requirements vary tremendously," Barnett pointed out. "Let's face it — our friend's physical makeup was quite different from ours."

"That's not so good," Agee said.

The three men looked at each other. In the silence that followed, they heard a faint, ominous sound.

"What was that?" Victor yelped, yanking out his blaster.

"Shut up!" Barnett shouted.

They listened. Barnett could feel the hairs lift on the back of his neck as he tried to identify the sound.

It came from a distance. It sounded like metal striking a hard non-metallic object.

The three men looked out the port. In the last glow of sunset, they could see the main port of Endeavor I was open. The sound was coming from the ship.

"It's impossible," Agee said. "The freeze-blasters —"

"Didn't kill him," Barnett finished.

"That's bad," Agee grunted. "That's very bad."

Victor was still holding his blaster. "Captain, suppose I wander over that way —"

Barnett shook his head. "He wouldn't let you within ten feet of the lock. No, let me think. Was there anything on board he could use? The piles?"

"I've got the links, Captain," Victor said.

"Good. Then there's nothing that —"

"The acid," Agee interrupted. "It's powerful stuff. But I don't suppose he can do much with that stuff."

"Not a thing," Barnett said. "We're in this ship and we're staying here. But get it off the ground now."

Agee looked at the instrument panel. Half an hour ago, he had almost understood it. Now it was a cunningly rigged death trap — a booby trap, with invisible wires leading to destruction.

The trap was unintentional. But a spaceship was necessarily a machine for living as well as traveling. The controls would try to reproduce the alien's living conditions, supply his needs.

That might be fatal to them.

"I wish I knew what kind of planet he came from," Agee said unhappily. If they knew the alien's environment, they could anticipate what his ship would do.

All they knew was that he breathed a poisonous yellow gas.

"We're doing all right," Barnett said, without much confidence. "Just dope out the drive mechanism and we'll leave everything else alone."

Agee turned back to the controls.

Barnett wished he knew what the alien was up to. He stared at the bulk of his old ship in the twilight and listened to the incomprehensible sound of metal striking non-metal.

Kalen was surprised to find that he was still alive. But there was a saying among his people —"Either a Mabogian is killed fast or he isn't killed at all." It was not at all — so far.

Groggily, he sat up and leaned against a tree. The single red sun of the planet was low on the horizon and breezes of poisonous oxygen swirled around him. He tested at once and found that his lungs were still securely sealed. His life-giving yellow air, although vitiated from long use, was still sustaining him.

But he couldn't seem to get oriented. A few hundred yards away, his ship was resting peacefully. The fading red light glistened from its hull and, for a moment, Kalen was convinced that there were no aliens. He had imagined the whole thing and now he would return to his ship…

He saw one of the aliens loaded down with goods, enter his vessel. In a little while, the airlocks closed.

It was true, all of it. He wrenched his mind back to grim realities.

He needed food and air badly. His outer skin was dry and cracked, and in need of nutritional cleaning. But food, air and cleansers were on his lost ship. All he had was a single red kerla nut and the thetnite bomb in his body pouch.

If he could open and eat the nut, he could regain a little strength. But how could he open it?

It was shocking, how complete his dependence on machinery had been! Now he would have to find some way of doing the most simple, ordinary, everyday things — the sort of things his ship had done automatically, without the operator even thinking about them.

Kalen noticed that the aliens had apparently abandoned their own ship. Why? It didn't matter. Out on the plain, he would die before morning. His only chance for survival lay inside their ship.

He slid slowly through the grass, stopping only when a wave of dizziness swept over him. He tried to keep watch on his ship. If the aliens came after him now, all would be lost. But nothing happened. After an eternity of crawling, he reached the ship and slipped inside.

It was twilight. In the dimness, he could see that the vessel was old. The walls, too thin in the first place, had been patched and repatched. Everything spoke of long, hard use. He could understand why they wanted his ship. Another wave of dizziness swept over him. It was his body's way of demanding immediate attention.

Food seemed to be the first problem. He slipped the kerla nut out of his pouch. It was round, almost four inches in diameter, and its hide was two inches thick. Nuts of this sort were the main ingredient of a Mabogian spaceman's diet. They were energy-packed and would last almost forever, sealed.

He propped the nut against a wall, found a steel bar and smashed down on it. The bar, striking the nut, emitted a hollow, drum-like sound. The nut was undamaged.

Kalen wondered if the sound could be heard by the aliens. He would have to chance it. Setting himself firmly, he flailed away. In fifteen minutes, he was exhausted and the bar was bent almost in half.

The nut was undamaged.

He was unable to open the nut without a Cracker, a standard device on every Mabogian ship. No one ever thought of opening a nut in any other way.

It was terrifying evidence of his helplessness. He lifted the bar for another whack and found that his limbs were stiffening. He dropped the bar and took stock.

His chilled outer hide was hampering his motions. The skin was hardening slowly into impervious horn. Once the hardening was completed, he would be immobilized. Frozen in position, he would sit or stand until he died of suffocation.

Kalen fought back a wave of despair and tried to think. He had to treat his skin without delay. That was more important than food. On board his own ship, he would wash and bathe it, soften it and eventually cure it. But it was doubtful whether the aliens carried the proper cleansers.

The only other course was to rip off his outer hide. The second layer would be tender for a few days, but at least he would be mobile.

He searched on stiffening limbs for a Changer. Then he realized that the aliens wouldn't have even this piece of basic apparatus. He was still on his own.