But Lucky said, "We must get Summers, and you know why."

With lo growing large-sized once again in the visi-plate, Lucky said thoughtfully, "It's not entirely certain we can find him, Bigman."

Bigman said incredulously, "You don't think the Sirians actually picked him up, do you?"

"No, but Io's a big place. If he wanders off to some rendezvous, we might never locate him. I'm counting on his staying put. He'd have to carry air, food, and water with him if he moved, so it would be most logical for him to stay put. Particularly when he'd have no reason to expect us to come back."

Bigman said, "We should have known it was that cobber all along, Lucky. He tried to kill you first thing. Why should he want to do that, if he weren't playing along with the Sirians?"

'True enough, Bigman, but remember this: we were looking for a spy. Summers couldn't be the spy. He had no access to the leaked information. Once it was clear to me that the spy was a robot, that cleared Summers on another account. The V-frog had detected emotion

in him, so he couldn't be a robot and therefore couldn't be the spy. Of course that didn't prevent him from be-ing a traitor and saboteur, and I should not have allowed the search for a spy to blind me to that possibility."

He shook his head and added, "This seems to be a case riddled with disappointment. If it had been anyone else but Norrich who had covered for Summers, we would have had our robot. The trouble is that Norrich is the only man who could have had convincingly innocent reason to co-operate with Summers. He was friendly with Summers; we know that. Then, too, Norrich could innocently be ignorant that Summers never returned before take-off. After all, he's blind."

Bigman said, "Besides which, he showed emotion, too, so he can't be the robot."

Lucky nodded. "True enough." Yet he frowned and grew silent.

Down, down they came to Io's surface, landing almost in the marks of their previous take-off. The dots and smeared shadows in the valley resolved themselves into the equipment they had set up as they approached.

Lucky was surveying the surface intently through the visiplate. "Were any air tights left behind on Io?"

"No," said the commander.

"Then we may have our man. One air tight, as you may notice, is fully expanded behind that rock formation. Do you have the list of material unaccounted for 0n board?"

The commander delivered a sheet of paper without comment, and Lucky studied it. He said, "Bigman and I will go out after him. I doubt that we'll need help."

The tiny sun was high in the sky, and Bigman and Lucky walked on their own shadows. Jupiter was a thinnish crescent.

Lucky spoke on Bigman's wave length. "He must have seen the ship unless he's sleeping."

"Or unless he's gone," said Bigman.

"I doubt that he's gone."

And almost at once Bigman cried, "Sands of Mars, Lucky, look up there!"

A figure appeared at the top of the line of rock. It stood out blackly against the thinning yellow line of Jupiter.

"Don't move," came a low, tired voice on Lucky's own wave length. "I'm holding a blaster."

"Summers," said Lucky, "come down and surrender."

A note of bitter mockery entered the other's strained voice. "I guessed the right wave length, didn't I, Councilman? Though it was an easy guess from the size of your friend… Get back to your ship or I'll kill you both."

Lucky said, "Don't bluff pointlessly. At this distance you couldn't hit us in a dozen tries."

Bigman added with tenor fury, "And I'm armed, too, and I can hit you even at this distance. Just remember that and don't even move a finger near the activating button."

Lucky said, "Throw down your blaster and surrender."

"Never!" said Summers.

"Why not? To whom are you being loyal?" Lucky demanded. "The Sirians? Did they promise to pick you up? If so, they lied to you and betrayed you. They're not worth loyalty. Tell me where the Sirians' base in the Jupiter system is located."

"You know so much! Figure it out for yourself."

"What subwave combination do you use to contact them?"

"Figure that out, too… Don't move any closer."

Lucky said, "Help us out now, Summers, and I'll do my best to get you mild treatment on Earth."

Summers laughed weakly. "The word of a councilman?"

"Yes."

"I wouldn't take it. Get back to your ship."

"Why have you turned against your own world, Summers? What have the Sirians offered you? Money?"

"Money!" The other's voice was suddenly furious. "Do you want to know what they offered me? I'll tell you. A chance at a decent life." They could hear the tiny gritting sound Summers made as his teeth ground together. "What did I have on Earth? Misery all my life. A crowded planet with no decent chance at making a name and a position for myself. Everywhere I went I was surrounded by millions of people clawing at each other for existence, and when I tried to claw also, I was put in jail. I made up my mind that if ever I could do anything to get back at Earth, I would."

"What do you expect to get from Sirius in the way of a decent life?"

"They invited me to emigrate to the Sirian planets, if you must know." He paused, and his breathing made small whistling noises. "New worlds out there. Clean worlds. There's room for men there; they need men and talent. I'd have a chance there."

"You'll never get there. When are they coming for you?"

Summers was silent

Lucky said, "Face it, man. They're not coming for you. They have no decent life for you; no life at all for you. Only death for you. You expected them before this, didn't you?"

"I didn't."

"Don't lie. It won't improve the situation for you. We've checked the supplies missing from the Jovian Moon. We know exactly how much oxygen you smuggled off the ship. Oxygen cylinders are clumsy things to carry even under Io's gravity when you have to sneak them off without being caught and in a hurry. Your air supply is almost gone now, isn't it?"

"I have plenty of air," said Summers.

Lucky said, "I say it's almost gone. Don't you see the Sirians aren't coming for you? They can't come for you without Agrav and they haven't got Agrav. Great Galaxy, man, have you let yourself get so hungry for the Sirian worlds that you'll let them kill you in as open and crude a double-cross as I've ever seen? Now, tell me, what have you done for them?"

Summers said, "I did what they asked me to do and that wasn't much. And if I have any regrets," he shouted in sudden, breathless bravado, "if s only that I didn't get the Jovian Moon. How did you get away, anyway? I fixed it. I fixed the rotten, slimy…" he ended, choking.

Lucky motioned to Bigman and broke into the soaring lope characteristic of running on low-gravity worlds. Bigman followed, veering off so as not to offer a single target.

Summers' blaster came up and made a thin popping sound, all that was possible in Io's thin wisps of atmosphere. Sand kicked up and around, and a crater formed yards from Lucky's fleeting figure.

"You won't catch me," Summers yelled with a kind of weak violence. "I'm not coming back to Earth. They'll come for me. The Sirians will come for me."

"Up, Bigman," said Lucky. He had reached the rock formation. Jumping upward, he caught a projection and hurled himself further upward. At sixth-normal gravity, a man, even in a space suit, could outdo a mountain goat in climbing.

Summers screamed thinly. His hands moved up to his helmet and he leaped backward and disappeared.

Lucky and Bigman reached the top. The rock formation was nearly sheer on the other side, with sharp outcroppings breaking the clifflike face. Summers was a spread-eagled figure, dropping slowly downward, striking against the face of the rock, and rebounding.