Commander Donahue said, "Major Levinson, then." His eyes darkened. "And yet I find that impossible to believe."

"Find what impossible to believe?" Lucky asked.

"That he is a robot. He's the man who took the report. He keeps our records. I know him well and I swear that he can't be a robot."

"We'll question him, Commander. And one thing-" Lucky's expression was somber. "Don't accuse him of being a robot; don't ask him if he's one or even imply that he might be one. Do nothing to make him feel he's under suspicion."

The commander looked astonished. "Why not?"

"The Sirians have a way of protecting their robots. Open suspicion may trigger some explosive device within the major if he is indeed a robot."

The commander exhaled explosively. "Space!"

Major Levinson showed the signs of strain that were universal among the men aboard the Jovian Moon, but he stood at brisk military attention. "Yes, sir."

The commander said cautiously, "Councilman Starr has a few questions to ask."

Major Levinson shifted to face Lucky. He was quite tall, topping even Lucky's inches, with fair hair, blue eyes, and a narrow face.

Lucky said, "All men were reported on board the Jovian Moon at the tune of take-off from Io, and you prepared that report. Is that right, major?"

"Yes, sir."

"Did you see each man individually?"

"No, sir. I used the intercom. Each man answered at take-off station or in his cabin."

"Each man? Did you hear each man's voice? Each individual voice?"

Major Levinson looked astonished. "I suppose so. That's not the sort of thing one remembers, really."

"Nevertheless it's quite important and I'm asking you to remember."

The major frowned and bent his head. "Well, now wait. Come to think of it, Norrich answered for Summers because Summers was hi the bathroom." Then, with a sudden spark of excitement, he added, "Hold on, they're looking for Summers right now."

Lucky held up a palm. "Never mind that, Major. Would you get Norrich and send him up?"

Norrich came in on Major Levinson's arm. He looked bewildered. He said, "Commander, no one seems to be able to find Red Summers. What's hap-pened to him?"

Lucky forestalled the commander's answer. He said, "We're trying to find out. Did you report Summers present when Major Levinson checked those aboard before we left Io?"

The blind engineer reddened. He said tightly, "Yes."

"The major says you said Summers was in the bathroom. Was he?"

"Well... No, he wasn't, Councilman. He had gotten off ship for a moment to pick up some item of equipment he had left behind. He didn't want the commander chewing him out-pardon me, sir-for carelessness, and he asked me to cover for him. He said he would be back well before take-off."

"Was he?"

"I... I thought... I had the impression he was. Mutt barked, I think, and I was sure Summers was coming back, but there isn't anything for me to do at take-off, so I was turning in for a nap and I guess I just didn't give the matter too much thought at the moment. Then there was the mess in the engine room almost right away, and after that there was no time to think of anything."

Panner's voice came over the central intercom with sudden loudness. "Warning to all men. We are taking off. Everyone to stations."

The Jovian Moon was in space again, lifting itself against Jupiter's gravity with powerful surges. It was expending energy at a rate that would have bankrupted five ordinary vessels and only the fault tremor in the sound of the hyperatomics remained to show that the ship's mechanism depended, in part, on makeshift devices.

Panner gloomily pondered on the poor showing the ship would now make energy-wise. He said, "As is, I'll get back with only seventy per cent of original energy, when it could have been eighty-five or ninety.

If we land on lo and make another take-off, we'll get back with only fifty. And I don't know if we can stand another take-off."

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.

Bigman said, "Let's get lam, Lucky," and jumped far outward, wide of the cliff. Lucky followed.

It would have been a killing leap on Earth, even on Mars. On Io it was little more than a tooth-jarring drop.

They hit with bent knees and let themselves roll to take up some of the force of impact. Lucky was on his feet first and made for Summers, who lay prone and unmoving.

Bigman came up panting. "Hey, that wasn't the easiest jump I- What's the matter with the cobber?"

Lucky said grimly. "He's dead. I knew his oxygen was low from the way he sounded. He was almost unconscious. It's why I rushed him."

"You could go a long time being unconscious," said Bigman.

Lucky shook his head. "He made sure. He really didn't want to be taken. Just before he jumped, he opened his helmet to id's poison air and he hit the cliff."

He stepped aside and Bigman caught a glimpse of the smashed face.

Lucky said, "Poor fool!"

"Poor traitor!" Bigman raged. "He might have had the answer and he wouldn't tell us. Now he can't tell us."

Lucky said, "He doesn't have to, Bigman. I think I know the answer now."