A yell of alarm that changed to a shriek of agony cut the air, coming from the southern border of camp. Another. The firing grew suddenly intense, lines of red and yellow tracer whipping out from the towers. A flare exploded overhead to disclose a shadow like a giant bat that swooped heavily across the barrier and fell upon a Mec just inside. The man's automatic rifle roared a futile, unaimed burst as he died. The Martians themselves Nick could not see.
Dazzled by the intermittent glare, he almost swam into the barrier without seeing it. Only the barrier itself saved him as the rising water engulfed another wire and the lethal current popped and sparked. With a heave of his shoulders he swung aside and glanced up. Ten or twelve feet of the fence's thirty foot height still projected above the surface.
He floated, tightening his mask until the nosepiece dug into his face. Then he pushed the clip down over the valve, and as the life-giving gas hissed out closed his eyes and let himself sink into the silt-filled, inky water.
Bubbles spurted around the edge of the mask and roared upward past his ears, but he found that by inhaling slowly he could breathe. His feet touched bottom and his legs sank in almost to the knees. The fine, dusty sand of Mars that had lain arid for so many centuries had changed to clinging, sticky mud. He pulled himself free and swam forward anxiously along the bottom.
One outstretched hand found the barrier. He felt the prick of the hooked, knife-edged barbs as they sank through the cloth with which he had wrapped his hands. He advanced the other more cautiously. Here below the surface the killing current of the barrier was dead, shorted away by the dirty water.
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.