When the thick, oily smoke thinned out, the smaller animals had fled into the fog. Mac sent out a squadron of fishmen, who destroyed the dying meat-eaters. If the bodies had been allowed to remain, the 'pedes would have used them as a food supply. The fishmen came back inside, and all the fog-wrapped world was silent. On noiseless feet, the oncoming army moved with impossible precision toward the camp. Twenty-five defenders against uncounted millions, with only a web of wiring and a concrete wall between them and the jaws of doom. And even if they won, victory would be no more than a truce.... * * * * * The six armies of centaurpedes met and fused. Narrower and narrower grew the gap between the mine and the unending wave of repulsive vermin. Then, when they were almost at the fence, the main army suddenly slowed down, and the two wings broke into double-swift march, advancing on both sides of the barrier. "Turn on the juice!" Mac snapped into his microphone. Abruptly, the fence began shooting off big blue sparks in the wet air. The main body of centaurpedes halted a few yards away and remained impassive. Inside, the fishmen stood frozen, staring in terror at the long, multi-legged animals, the round, intelligent-looking heads, the huge mandibles, and the upright shoulders with pairs of clever hands and arms. Behind the camp, the encircling wings met and joined. More advanced until the surrounding army was uniform in depth. Then, with a single movement, the black cataract flooded straight at the wire fence. "Hold your fire!" Mac yelled at his fishmen. Around the compound, he heard Swede and Al shouting the same order. But it was too much to expect of fear-tightened native nerves. Spasmodic bursts of fire spurted out. Undaunted, the horde pressed on against the fence. Crackling and flashing, the electrified wire suddenly flung out great streamers of sparks. The moist chitinous bodies shriveled into ashes. A stink of burned flesh polluted the heavy fog. Apparently at an inaudible signal, the entire mass of 'pedes fell back out of danger. MacAloon was awed. He knew that the rear of a human army, unable to see what was happening up front, would keep pushing forward. But a secret knowledge, impossible to men, made the centaurpedes act as a single entity. Looking along the fence, Mac could see detachments of 'pede scouts, moving warily toward the sparking barrier. While the army watched, the reconnoiterers experimentally touched the wire. A flash and they were destroyed, but not before serving their purpose. They had given the army a chance to analyze the fence's properties. Again the entire force moved forward, this time with more caution than before. MacAloon looked on anxiously, knowing they were aware of the danger. "Mac!" cried Al's voice. "What're they going to do?" "They're too smart to keep electrocuting themselves," said MacAloon tersely. "They must have a plan." "But what is it?"