Matson grinned coldly. The aliens were not invulnerable. If Mankind could be taught to fear and hate them, and if that emotion could be focussed, they never again would try to take this world. It would be sheer suicide. As long as Mankind kept its emotions it would be safe from this sort of invasion. But the problem was to teach Mankind to fear and hate. Shock would do it, but how could that shock be applied? The thought led inevitably to the only possible conclusion. The aliens would have to be killed, and in such a manner as to make humanity fear retaliation from the stars. Fear would unite men against a possible invasion, and fear would force men to reach for the stars to forestall retribution. Matson grinned thinly. Human nature couldn't have changed much these past years. Even with master psychologists like the Aztlans operating upon it, changes in emotional pattern would require generations. He sighed, looked into the anxious face of Seth Winters, and returned to the reality of the desert night. His course was set. He knew what he had to do. * * * * * He laid the rifle across his knees and opened the little leather box sewn to the side of the guncase. With precise, careful movements he removed the silencer and fitted it to the threaded muzzle of the gun. The bulky, blue excrescence changed the rifle from a thing of beauty to one of murder. He looked at it distastefully, then shrugged and stretched out on the mattress, easing the ugly muzzle through the hole in the brickwork. It wouldn't be long now.... He glanced upward through the window above him at the Weather Bureau instruments atop a nearby building. The metal cups of the anemometer hung motionless against the metallic blue of the sky. No wind stirred in the deep canyons of the city streets as the sun climbed in blazing splendor above the towering buildings. He moved a trifle, shifting the muzzle of the gun until it bore upon the sidewalks. The telescopic sight picked out faces from the waiting crowd with a crystal clarity. Everywhere was the same sheeplike placidity. He shuddered, the sights jumping crazily from one face to another,--wondering if he had misjudged his race, if he had really come too late, if he had underestimated the powers of the Aztlans. Far down the avenue, an excited hum came to his ears, and the watching crowd stirred. Faces lighted and Matson sighed. He was not wrong. Emotion was only suppressed, not vanished. There was still time! The aliens were coming. Coming to cap the climax of their pioneer work, to drive the first nail in humanity's coffin! For the first time in history man's dream of the brotherhood of man was close to reality.