Crag sighted the Red Dog party immediately—three figures plodding in single file toward Drone Baker. He saw with satisfaction that they had discarded the rocket launcher. He took that as a sign they believed the Aztec crew dead. He found a halfway comfortable sitting position, and settled back to await developments.

The distant figures moved across the plain with maddening slowness. From time to time he returned his eyes to the enemy rocket. It showed no signs of life. Once he debated taking the gamble of trying to reach it, but as quickly discarded the idea. Caught on the open plain and he'd be a gone gosling.

He waited.

After what seemed a long while, the invaders reached a point overlooking Drone Baker. One of the figures remained on a small rise overlooking the drone while the other two separated and approached it from different directions. The tactic disquieted him. It indicated that the newcomers were not entirely convinced that they were alone in Crater Arzachel.

After another interminably long time, the two figures approaching the rocket met at its base. They walked around the rocket several times, then struck out, this time toward Drone Charlie. Their companion left his lookout point and cut across the plain to join them.

Crag squirmed uncomfortably. He was tired and hungry; his muscles ached from the constriction of the suit. His body was hot and clammy, and perspiration from his brow stung his eyes. He sighed, wishing he had a cigarette. Strange, he hadn't smoked in over a year but all at once the need for tobacco seemed overwhelming. He pushed the thought aside.

The invaders were strung out in single file, moving in a direction which brought them closer to his position. He shifted to a point below the crest, moving slowly to avoid detection. Their path crossed his field of vision at a distance of about half a mile. At the closest point he saw they carried rifles in shoulder slings. He took this as another indication they suspected the presence of survivors. The invaders stopped and rested at a point almost opposite him. He fidgeted, trying to get his body into a more comfortable position.

Finally they resumed their trek. Before they reached the drone they halted. One man remained in the cover of a spur of rock while the other two separated and advanced on the drone from different directions. Crag cursed under his breath. They certainly weren't going to be sitting ducks. Perhaps it was just a precaution. Simply good infantry tactics, he told himself, but it still raised a complication.

He waited. The two invaders closed on the drone, meeting at its base. They evidently decided it was abandoned, for they left within a few minutes walking to join their waiting companion. After a short huddle they struck out in the direction of Bandit. This was the move he had waited for.

He withdrew to the lee side of the ridge and picked his way toward Bandit as rapidly as possible, taking care not to brush against the sharp slivers of rock. He drew near the rocket, thinking that the open hatch would be a dead giveaway. Still, there was no alternative. A fort without a gunport was no fort at all. He climbed to a spot close to the crest of the ridge and peered back in the direction of the invaders, startled to find they were nearer than he had supposed. He hastily withdrew his head, deciding it was too late to warn the others to abandon the rocket. If the invaders climbed straight up the opposite side of the ridge, they conceivably could catch his crew on the open plain. That made another complication.

He scanned the ridge. Off to his right a series of granite spurs jutted from the base rock in finger formation. He picked his way toward them, then descended until he found shelter between two rock outcroppings which gave him a clear view of Bandit. He checked his automatic rifle, moving the control lever to the semi-automatic position. The black rectangle that marked Bandit's hatch seemed lifeless.

He waited.

Long minutes passed. He cursed the eternal silence of the moon which robbed him of the use of his ears. A cannon could fire within an inch of his back and he'd never know it, he thought. He moved his head slightly forward from time to time in an effort to see the slope behind him. Nothing happened. His body itched intolerably from perspiration. He readjusted the suit temperature setting, gaining a slight respite from the heat. All at once he caught movement out of the corner of his face plate and involuntarily jerked his head back. He waited a moment, aware that his heart was pounding heavily, then cautiously moved forward. One of the invaders was picking his way down the slope in a path that would take him within thirty yards of his position. The man moved slowly, half-crouched, keeping his rifle cradled across his arm.

They know, he thought. The open hatch was the giveaway. He anxiously searched Bandit. No sign of life was visible. He gave silent thanks that the invaders had not lugged their rocket launcher with them. Prochaska, he knew, would be watching, crouched in the shadow of the hatch opening behind the heavy automatic rifle. He estimated the distance between the base of the slope and the rocket at 400 yards—close enough for Prochaska to pick off anyone who ventured onto the plain.

He waited while the invader passed abreast of him and descended to the base of the plain, taking cover in the rocks. He halted there and looked back. A few moments later Crag saw the second of the invaders moving down the slope about a hundred yards beyond his companion. He, too, stopped near the base of the rocks. Where was the third man? The same technique they used before, Crag decided. He would be covering his companions' advance from the ridge. That made it more difficult.

He studied the two men at the edge of the plain. It looked like a stalemate. They either had to advance or retreat. Their time was governed by oxygen. If they advanced, they'd be dead pigeons. Prochaska couldn't miss if they chose to cross the clearing. As it was, neither side could get a clear shot at the distance separating them, although the invaders could pour a stream of shells into the open hatch. But Prochaska would be aware of that danger and would have taken refuge to one side of the opening, he decided. There was another complication. The shells were heavy enough to perforate the rocket. Well, he'd worry about that later. He moved his head for a better view of the invaders.

The man nearest him had gotten into a prone position and was doing something with the end of his rifle. Crag watched, puzzled. Suddenly the man brought the rifle to his shoulder, and he saw that the end of the muzzle was bulged. Rifle grenade! Damn, they'd brought a regular arsenal. If he managed to place one in the open hatch, the Bandit crew was doomed. Heedless of the other two Red Dog crewmen, he stepped out between the shoulders of rock to gain freedom of movement and snapped his own weapon to his shoulder. He had trouble fitting his finger into the trigger guard. The enemy was spraddled on his stomach, legs apart, adjusting his body to steady his weapon.

Crag moved his weapon up, bringing the prone man squarely into his sights. He squeezed the trigger, feeling the weapon jump against his padded shoulder, and leaped back into the protective cover of rock. Something struck his face plate. Splinter of rock, he thought. The watcher on the ridge hadn't been asleep. He dropped to his knees and crawled between the rock spurs to gain a new position. The sharp needle fragments under his hands and knees troubled him. One small rip and he'd be the late Adam Crag. He finally reached a place where he could see the lower end of the ridge.

The man he'd shot was a motionless blob on the rocky floor, his arms and legs pulled up in a grotesque fetal position. The vulnerability of human life on the moon struck Crag forcibly. A bullet hole anywhere meant sudden violent death. A hit on the finger was as fatal as a shot through the heart. Once air pressure in a suit was lost a man was dead—horribly dying within seconds. A pinhole in the suit was enough to do it. His eyes searched for the dead man's companions. The ridge and plain seemed utterly lifeless. Bandit was a black canted monolith rising above the plain, seeming to symbolize the utter desolation and silence of Crater Arzachel. For a moment he was fascinated. The very scene portended death. It was an eery feeling. He shook it off and waited. He was finally rewarded by movement. A portion of rock near the edge of the plain seemed to rise—took shape. The dead man's companion had risen to a kneeling position, holding his rifle to his shoulder.

Crag raised his gun, wondering if he could hold the man in his sights. A hundred and fifty yards to a rifleman clothed in a cumbersome space suit seemed a long way. Before he could pull the trigger, the man flung his arms outward, clawing at his throat for an instant before slumping to the rocks. It took Crag a second to comprehend what had happened. Prochaska had been ready.

A figure suddenly filled the dark rectangle of Bandit, pointing toward the ridge behind Crag. He apparently was trying to tell him something. Crag scanned the ridge. It seemed deserted. He turned toward Bandit and motioned toward his faceplate. The other understood. His interphones crackled to life. Prochaska's voice was welcome.

"I see him," he broke in. "He's moving up the slope to your right, trying to reach the top of the ridge. Too far for a shot," he added.

Crag scrambled into a clearing and scanned the ridge, just in time to see a figure disappear over the skyline. He started up the slope in a beeline for the crest. If he could reach it in time, he might prevent the sniper from crossing the open plain which lay between the ridge and Red Dog. Cops and robbers, he thought. Another childhood game had suddenly been recreated, this time on the bleak plain of an airless alien crater 240,000 miles from the sunny Southern California lands of his youth.

Crag reached the ridge. The plain on the other side seemed devoid of life. In the distance the squat needle that was Red Dog jutted above the ashy plain, an incongruous human artifact lost on the wastelands of the moon. Only its symmetry distinguished it from the jagged monolithic structures that dotted this end of the crater floor. He searched the slope. Movement far down the knoll to his right caught his eye. The fugitive was trying to reach a point beyond range of Crag's weapon before cutting across the plain. He studied the terrain. Far ahead and to the left of the invader the crater floor became broken by bizarre rock formations of Backbone Ridge—a great half-circle which arced back toward Red Dog. He guessed that the fantastic land ahead was the fugitive's goal.

He cut recklessly down the opposite slope and gained the floor of the crater before turning in the direction he had last seen the invader. He cursed himself for having lost sight of him. Momentarily, he slowed his pace, thinking he was ripe for a bushwhacking job. His eyes roved the terrain. No movement, no sign of his quarry. He moved quickly, but warily, attempting to search every inch of the twisted rock formations covering the slope ahead. His eye detected movement off to one side. At the same instant a warning sounded in his brain and he flung himself downward and to the side, hitting the rough ground with a sickening thud. He sensed that the action had saved his life. He crawled between some rock outcroppings, hugging the ground until he reached a vantage point overlooking the area ahead. He waited, trying to search the slope without exposing his position. Minutes passed.

He tossed his head restlessly. His eyes roved the plain, searching, attempting to discern movement. No movement—only a world of still life-forms. The plain—its rocks and rills—stretched before him, barren and endless. Strange, he thought, there should be vultures in the sky. And on the plain creosote bushes, purple sage, cactus ... coyotes and rattlesnakes.

But ... no! This was an other-world desert, one spawned in the fires of hell—a never-never land of scalding heat and unbelievable cold. He thought it was like a painting by some mad artist. First he had sketched in the plain with infinite care—a white-black, monotonous, unbroken expanse. Afterward he had splashed in the rocks, painting with wild abandon, heedless of design, form or structure, until the plain was a hodgepodge of bizarre formations. They towered, squatted, pierced the sky, crawled along the plain like giant serpents—an orgy in rock without rhyme or reason. Somewhere in the lithic jungle his quarry waited. He would flush him out.

He thought that the sniper must be getting low on oxygen. He couldn't afford to waste time. He had to reach Red Dog soon—if he were to live. Crag checked his oxygen meter and began moving forward, conscious that the chase would be governed by his oxygen supply. He'd have to remember that.

He reached a clearing on the slope just as the sniper disappeared into the rock shadows on the opposite side. He hesitated. Would the pursued man be waiting ... covering the trail behind him? He decided not to chance crossing it and began skirting around its edge, fretting at the minutes wasted. His earphones crackled and Prochaska's voice came, a warning through the vacuum:

"Nagel says your oxygen must be low."

He glanced at the indicator on his cylinder. Still safe. He studied the rocks ahead and told Prochaska:

"I've got to keep this baby from reaching Red Dog."

"Watch yourself. Don't go beyond the point of no return." Prochaska's voice held concern.

"Stop worrying."

Crag pushed around the edge of the clearing with reckless haste. It was hard going and he was panting heavily long before he reached the spot where he had last seen the sniper. He paused to catch his breath. The slope fell away beneath him, a miniature kingdom of jagged needle-sharp rock. There was no sign of the fugitive. The plain, too, was devoid of life. He descended to the edge of the clearing and picked his way through the debris of some eon-old geologic catastrophe. Ahead and to the left of the ridge, the plain was broken by shallow rills and weird rock outcroppings. Farther out Backbone Ridge began as low mounds of stone, becoming twisted black stalagmites hunched incongruously against the floor of the crater, ending as jagged sharp needles of rock curving over the plain in a huge arc.

A moment later he caught sight of his quarry. The invader had cut down to the edge of the plain, abandoning the protection of the ridge, making a beeline for the nearest rock extrusion on the floor of the crater. Too far away for a shot. Crag cursed and made a quick judgment, deciding to risk the open terrain in hopes of gaining shelter before the sniper was aware of his strategy.

He abandoned the protection of the slope and struck out in a straight line toward the distant mounds on the floor of the crater, keeping his eyes on the fugitive. They raced across the clearing in parallel paths, several hundred yards apart. The sniper had almost reached the first rocks when he glanced back. He saw Crag and put on an extra burst of speed, reaching the first rocks while Crag was still a hundred yards from the nearest mound. Crag dropped to the ground, thankful that it was slightly uneven. At best he'd make a poor target. He crawled, keeping his body low, tossing his head in an effort to shake the perspiration from his eyes.

"How you doing, skipper?" It was Prochaska. Lousy, Crag thought. He briefed him without slowing his pace.

The ashy plain just in front of him spurted in little fountains of white dust. He dropped flat on his belly with a gasp.

"You all right?"

"Okay," Crag gritted. "This boy's just using me for target practice." Prochaska's voice became alarmed. He urged him to retreat.

"We can get them some other way," he said.

"Not if they once get that launcher in operation. I'm moving on." There was a moment of silence.

"Okay, skipper, but watch yourself." His voice was reluctant. "And watch your oxygen."

"Roger." He checked his gauge and hurriedly switched to the second cylinder. Now he was on the last one. The trick would be to stretch his oxygen out until the chase was ended—until the man ahead was a corpse.

He clung to the floor of the crater, searching for shelter. The ground rose slightly to his right. He crawled toward the rise, noting that the terrain crested high enough to cut his view of the base of the rocks. Satisfied that he was no longer visible, he began inching his way toward the nearest mounds.