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. CHAPTER 16