They ate hastily, in the awakening light of sunrise. They ran away from the sound of the machine, and it lessened in the distance. It was the middle of the morning when they heard it again. Nelson judged it to be roughly a mile away and to the west. He waited a minute, listening. It seemed to be describing a search pattern curve that swung in front of their path. He decided to double back and around to miss it. The undergrowth was thick in this part of the forest. They made their way through the bushes and waist-high grasses, being as careful as possible not to leave too many signs of their passing. Glynnis' shorts and thin blouse weren't much protection against the thorns or the recoiling limbs of bushes but she didn't complain. Gradually the forest became mostly trees again. They found a path some animal had made and followed it. When they came to the clearing, Nelson almost didn't see the thing in the air. He heard Glynnis gasp behind him, and with a start, glanced around. She was staring at something in front of them, and in the air. He looked where she was staring and saw the air robot hovering near the edge of the clearing. It was about two feet long, slender, metallic and smooth. Nelson knew though that it was alert and that receptors built into its skin were registering their presence. It hovered about ten feet above the ground, some twenty feet from them, making no noise. Sky robots made noise only when they were moving at a fairly good speed. They had fled the noise of one only to be trapped in the silence of another. Suddenly, Glynnis was shouting, "It's one of them!" Nelson turned to see her level her gun, and before he could stop her a white hot streamer lashed out at the robot and engulfed it. "No," he shouted, too late. The machine took the blast turning cherry red and bobbing lightly in the air for a moment before energy compensators and stabilizers adjusted to the effects of the blast. The machine turned back to its lustrous silver color and there was a low hum as it righted itself gracefully then swung around, into the center of the clearing to get a better focus on them. "It doesn't even have a mark on it," Glynnis said, in a low tone, moving closer to Nelson and laying one hand on his shoulder. "No. But don't worry; it can't hurt us. We've got to figure some way to get out of here and leave it behind." He turned and gently guided her toward the trees. When they were in the dubious shelter of the trees, Nelson stopped and tried to figure a way out. He could see the machine hanging in the center of the clearing on invisible lines of force, turning slightly to find them in the dense growth, then, with one end pointed at them, bobbing slightly with the low breeze. "What's it doing?" Glynnis asked. There was superstitious awe in her voice that annoyed Nelson. "Sending a signal to the patrol. We don't have much time before they get here." "But if the machine can't be shot down what can we do?"