In one smooth rapid motion Dworn switched off the pump, and spun the drill control. As the mechanism telescoped back into place, he gunned his engine, and the beetle shot backward and spun round to face the oncoming noise. A squarish black silhouette loomed high on the slope above the overhanging bank, which rose so steeply that a stone loosened by turning treads bounded with a clang off the beetle's armor in the wash below. The caterpillar halted momentarily, engine grumbling to take in the scene. Dworn didn't linger to learn its reaction at spying a looter. A snap shot from his turret gun exploded directly in front of the other machine, throwing up a cloud of dust and--he hoped--confusing its crew. And the beetle was fleeing around the bend in the stream bed, keeping close to the high bank. A score of yards past the turning, intuition of danger made Dworn swerve sharply. An instant later, the ground blew up almost in his face--the bend had brought him into view, under the guns of the enemy above. He wrenched the beetle around in a skidding turn and raced back for the bend where the overhang afforded shelter. Another shell and another crashed into places he had just left, and then he was safe--for the moment. But it was an uncomfortable spot. The caterpillar rumbling wrathfully on the slope above him, couldn't see him as long as he hugged the bank, undercut by the water that flowed here in the rainy season; but, by the same token, he couldn't make a dash for safety without running the gauntlet of a murderous fire in the all-too-narrow way the stream bed offered. In open country, he would not have hesitated to count on his ability to outmaneuver and outshoot the caterpillar ... but here he was neatly trapped. And it was nerve-racking to be unable to see what the enemy was about. It seemed to have halted, judging the situation just as he had been doing. Now, though, he heard its engine speed up again, and the grinding of its treads came unmistakably closer. His ears strained to gauge its advance as it came lurching down the slope, till it sounded only a few feet away and Dworn braced himself to shoot fast and straight if it started coming down over the bank. Then it paused again, and sat idling, hoping no doubt that he would panic and show himself. He didn't. The caterpillar's engine raced up once more and began to labor under a heavy load. There was an increasing clatter of falling stones. Then Dworn remembered the great digging-blade it carried, and realized what it was going to try. Ten feet to his right the bank began giving way. Tons of rubble thundered into the gully. Dworn winced and moved away as far as he dared. He heard the caterpillar back and turn, then it snarled with effort once more and another section of the overhang caved in with a grinding roar.