Time to go. Carter readied himself for another jump. This one would be horrible. He'd be taking off with the buggy canted thirty degrees backward...

Wait a minute.

There was something wrong with that picture of Alf's buggy as it

rolled toward the lock surrounded by trotting men. Definitely something wrong there. But what?

It would come to him. He gripped the jet throttle and readied his other hand to flip on the gyros the moment he was airborne.

-Alf had planned so carefully. How had he come away with one O-tank too few?

And-- if he really had everything planned, how did Al f expect to

get Carter's tanks if Carter crashed?

Suppose Carter crashed his buggy against a hill, right now, on his second jump. How would Alf know? He wouldn't, not until nine o'clock came and Carter hadn't shown up. Then he'd know Carter had crashed somewhere. But it would be too late!

Unless Alf had lied.

That was it, that was what was wrong with his picture of Alf in the vehicular airlock. Put one O-tank in the air bin and it would stand out like a sore thumb. Fill the air bin and then remove one tank, and the hole in the hexagonal array would show like Sammy Davis III on the Berlin Nazis football team! There had been no such hole.

Let Carter crash now, and Alf would know it with four hours in which to search for his buggy.

Carter swung his headlights up to normal position, then moved the buggy backward in a dead-slow half circle. The buggy swayed but didn't topple. Now he could move down behind his headlights...

Nine o'clock. If Carter was wrong then he was dead now. Even now Alf might be unfastening his helmet, his eyes blank with the ultimate despair, still wondering where Carter had got to. But if he was right...

Then Alf was nodding to himself, not smiling, merely confirming a guess. Now he was deciding whether to wait five minutes on the chance that Carter was late, or to start searching now. Carter sat in his dark cabin at the foot of the black mountains, his left hand clutching a wrench, his eyes riveted on the luminous needle of the direction finder.

The wrench had been the heaviest in his toolbox. He'd found nothing sharper than a screwdriver, and that wouldn't have penetrated suit fabric.

The needle pointed straight toward Alf

And it wasn't moving.

Alf had decided to wait.

How long would he wait?

Carter caught himself whispering, not loudly. Move, idiot. You've

got to search both sides o f the range. Both sides and the top. Move.

Move!

Ye gods! Had he shut off his radio? Yes, the switch was down.

Move.

The needle moved. It jerked once, infinitesimally, and was quiet.

It was quiet a long time-seven or eight minutes. Then it jerked in the opposite direction. Alf was searching the wrong side of the hills!

And then Carter saw the flaw in his own plan. Alf must now assume he was dead. And if he, Carter, was dead, then he wasn't using air. Alf had two hours extra, but he thought he had four!

The needle twitched and moved-a good distance. Carter sighed and closed his eyes. Alf was coming over. He had sensibly decided to search this side first; for if Carter was on this side, dead, then Alf would have to cross the range again to reach home.

Twitch.

Twitch. He must be at the top.

Then the long, slow, steady movement down.

Headlights. Very faint, to the north. Would Alf turn north?

He turned south. Perfect. The headlights grew brighter... and Carter waited, with his buggy buried to the windshield in the sand at the base of the range.

Alf still had the flare gun. Despite all his certainty that Carter was dead, he was probably riding with the gun in his hand. But he was using his headlights, and he was going slowly, perhaps fifteen miles per hour.

He would pass... twenty yards west...

Carter gripped the wrench. Here he comes.

There was light in his eyes. Don't see me. And then there wasn't. Carter swarmed out of the buggy and down the sloping sand. The headlights moved away, and Carter was after them, leaping as a Moonie leaps, both feet pushing at once into the sand, a second spent in flying, legs straddled and feet reaching forward for the landing and another leap.

One last enormous kangaroo jump-and he was on the O-tanks, falling on knees and forearms with feet lifted high so the metal wouldn't clang. One arm landed on nothing at all where empty O-tanks were missing. His body tried to roll off onto the sand. He wouldn't let it.

The transparent bubble of Alf's helmet was before him. The head inside swept back and forth, sweeping the triangle created by the headlights.

Carter crept forward. He poised himself over Alf's head, raised the wrench high, and brought it down with all his strength.

Cracks starred out in the plastic. Alf looked up with his eyes and mouth all wide open, his amazement unalloyed by rage or terror. Carter brought the weight down again.

There were more cracks, longer cracks. Alf winced and -finally brought up the flare gun. Carter's muscles froze for an instant as he looked into its hellish mouth. Then he struck for what he knew must be the last time.

The wrench smashed through transparent plastic and scalp and skull. Carter knelt on the O-tanks for a moment, looking at the unpleasant thing he'd done. Then he lifted the body out by the shoulders, tumbled it over the side, and climbed into the cabin to stop the buggy.

It took him a few minutes to find his own buggy where he'd buried it in the sand. It took longer to uncover it. That was all right. He had plenty of time. If he crossed the range by twelve-thirty he would reach bubbletown on the last of his air.

There would be little room for finesse. On the other hand, he would be arriving an hour before dawn. They'd never see him. They would have stopped expecting him, or Alf, at noon tomorrow-even assuming they didn't know Alf had refused to turn back.

The bubble would be empty of air before anyone could get into a suit.

Later he could repair and fill the bubble. In a month Earth would hear of the disaster: how a meteorite had touched down at a corner of the dome, how John Carter had been outside at the time, the only man in a suit. They'd take him home and he could spend the rest of his life trying to forget.

He knew which tanks were his empties. Like every man in town,

he had his own method of arranging them in the air bin. He dumped six and stopped. It was a shame to throw away empties. The tanks were too hard to replace.

He didn't know Alf's arrangement scheme. He'd have to test Alf s empties individually.

Already Alf had thrown some away. (To leave space for Carter's tanks?) One by one, Carter turned the valve of each tank. If it hissed, he put it in his own air bin. If it didn't, he dropped it.

One of them hissed. Just one.

Five O-tanks. He couldn't possibly make a thirty-hour trip on five O-tanks.

Somewhere, Alf had left three O-tanks where he could find them again. Just on the off chance: just in case something went terribly wrong for Alf, and Carter captured his buggy, Carter still wouldn't go home alive.

Alf must have left the tanks where he could find them easily. He must have left them near here; for he had never been out of Carter's sight until Carter crossed the range, and furthermore he'd kept just one tank to reach them. The tanks were nearby, and Carter had just two hours to find them.

In fact, he realized, they must be on the other side of the range. Alf hadn't stopped anywhere on this side.