Madsen blinked at him and started to rise. He was on one knee, when suddenly, he turned his head in a listening attitude. Morley had heard the distant hum, too, and was standing stock still, an anxious frown on his gaunt face. Madsen was on the verge of scrambling to his feet, when Morley spoke. "Don't move." "What's the--?" "Shut up, for God's sake. Don't stir." He was trembling, his bony features white as paper under their coating of grime. Madsen froze, wordless. Sailing through the tall grass, straight toward them, came one of the gray antelope-like creatures. It passed within twenty feet. They could see the heaving flanks, the foam on its muzzle, the rolling, terror stricken eyes. Close behind, and closing in rapidly, came the origin of the hum. It was a host of tiny iridescent flying creatures, no larger than bumblebees. They streaked by, green and crimson winged gems, the hum rising to a vicious crescendo. The chase ended a hundred yards away. As the cloud struck, the antelope screamed, a lone cry of agony and despair. It staggered once, tried to leap forward, staggered again, was down. There was a threshing, a violent movement of the grass, then silence. IV A quarter of an hour passed before a rising hum announced the ending of the feast. The component parts of the cloud took flight, coalesced into a group, vanished into the distance. Madsen broke first, heading for the remains of the antelope, with Morley close behind. The animal lay in a heap, drained of every drop of blood, its punctured eyes staring sightlessly at the empty heavens. "Meat," babbled Madsen. "Chops, steak, liver, heart." "Shut up," Morley said curtly, "and start a fire." He bent to the butchering. They ate, new life flooding into them. They were suddenly deeply conscious of the incredible sensation of being fed, of resting with a full stomach, of enjoying a reprieve that might be a pardon. Madsen stopped picking his teeth for a moment. "Did you know what those things were?" he asked. "Sure. Sangres, Valdez called them. Means bloody in Spanish. They're blood drinkers. There's one thing, though, you're pretty safe if you don't move. Those sweet little birds--and they are birds, as a matter of fact--hunt by sight." Madsen was silent. Then he laughed, and turned to eye the remains of the antelope fondly. "And to think we didn't even have to bleed it," he said. "When we get back, you might recommend some books for me to read, if you feel like doing a good turn." Morley was laughing, too. "It's a deal."