He drew himself downward, hand over hand along the closely spaced wires, down to where the barrier met the ground. He probed at the mud, holding himself in place with one hand. Wires. And at full arm's depth in the mud, still wires. He hooked his feet into the fence and dug with both hands, flinging the gooey muck aside in great, swirling gobs until the water grew thick and viscid around him. More strands of wire. He dug more frantically, hanging head down in the hole he had made. And then his clawing fingers encountered the solid rock into which the steel supports of the barrier were anchored. It was impossible to dig under that. A trickle of muddy water seeped into the mask, stinging the lining of his nose and making him want to sneeze. With an effort he extracted himself from the sticky burrow and clung to the ground level strands until the spasm passed. The hissing tone of the compressed oxygen was perceptibly lower. * * * * * Gently he grasped one strand with both cloth-wrapped hands, spreading his fingers in an attempt to avoid the barbs. But this was no ordinary barbed wire and the spacing of the evilly sharp, machine-finished prongs was such that one still pressed against each palm. His heavy boots protected his feet as he braced them against the adjoining strand. He brought his powerful back and leg muscles into play, ignoring the pain that lanced through his hands. The wires gave a fraction of an inch. He pulled again. The wires had been four inches apart; now they were almost six. At the third pull he could feel the barb in his left hand touch bone with a grating rasp, but the wires stretched still further. Again and again he tugged, resting only when he grew dizzy with pain. And then the oxygen was gone. He had just time to gulp in one last lungful as the hissing died and the bubbles around his face stopped. Once more he heaved at the wires, using every ounce of power his body could muster. Then, holding his breath, he rolled sideways into the gap he had created. The slackened wires sagged down and the cruel barbs bit into his chest and back and legs. He winced at the pain as he tore his hands loose from the deeply embedded prongs, then pulled the wires away from his chest and rolled his body further into the opening. The points dug into his chest again while he moved one leg and then the other. When he knew he could hold his breath only a few seconds more he broke clear with a lurch that left bleeding furrows across his body and floated dizzily toward the surface. One hand whipped the useless, empty oxygen bottle from his face. He sucked in the thin air of Mars with harsh, rasping, grateful breaths as he broke surface, glancing around to restore his sense of direction. He was inside the barrier.