 What did the beings use to ensure they killed every human?
There should be an epitaph for every man, big or little, but a really grand and special one for Loner Charlie. A year ago she had been unattainable, a face to conjure with in erotic dreams, far beyond his ken. Meanings and answers to his questions slithered out of his reach. He touched buttons by the edge of the bed and the illumination quieted to a soft glow, wrapping her in a radiant halo. New York lay quietly below him. It was the hour of indecision when day has not quite made up its mind to leave and night has not yet attacked in force. She would have given herself to any man— His thoughts beat a rapid crescendo, activating emotions, stimulating sensations of angry rage. In spite of the sharp pain that raced through his system, in spite of the bright, warm, red stream that trickled down his face, he knelt by the window for several minutes. " On sudden impulse he switched it on, turned the volume up full, and in grim jest left it playing Rachmaninoff's Isle of the Dead on full automatic. Shop fronts smashed, stores looted, gyro-cars wrecked, proud buildings defaced. Buildings were taller, men were healthier, most of the problems of humanity seemed licked, or nearly so. It was a time of free power, each small unit of population, each section of town operating on perpetual, ever-lasting, automatic atomic piles. Sales of poison dropped, scientific laboratories chained to a perpetual rodent-cycle began to complain bitterly.
 The Bureau's Index
 Charles's brain-waves  The Bureau's Index  A machine they brought from their home planet  Spies throughout the world