"That's right," he nodded. "Only one. We wanted to create panic and one will do that. When it goes off, that's all we need. The rest of the world will hear about it seconds later. And then the flight will be on." He paused. "You don't think that people--anywhere--are going to remain in their cities, do you? All the police, all the commissars in existence, couldn't make them do that. And then the air fleets will spring into action. One fleet because it demands vengeance, and the other because the only defense is a good offense, as the ape politicians are so fond of saying." He shrugged. "You see? It really only takes one for disaster." Stan gathered his muscles for one last lunge.... Tanner caught the movement and raised his eyebrows. "You wouldn't want to do that, Martin. For one reason, I've got Avis. And for another, it would be too late. The blast went off ten seconds ago." He waved and stepped into the blackness. Stan reeled over to the set and dialed Chicago. The sheet of blackness formed, wavered, and then faded back to the edges of the hoop. He had lost, Stan thought, dazed. The city he had been born and raised in was one with the drifting atoms of the air. Tanner had won, completely. And Tanner had Avis. Stan huddled in the center of the room, his mind a melee of flickering thoughts. Then a noise at the window caught his ear. The noise of doors slamming and the starting of a thousand automobiles and people running through the streets. He didn't bother to look--he knew what it was. The exodus of a billion people from ten thousand towns and cities was on the way. There was six hours to go before the start of the brief, abortive war. Six hours before the air fleets would arrive at their destination. A day later the Thuscan fleet would settle from the skies to begin the mopping up operation, the operation that would change the face of a green, water world to a world that would be another colony planet for Thusca. A world in which the human race would play no part. _And there was the matter of the girl...._ * * * * * The noise outside the street was a steady roar, now. The street was gorged with people on foot and on bicycles and in automobiles, fighting to get out of the city. He could hear screams and curses and over all, the faint crackle of flames. In a few hours, the city would be a roaring inferno, he thought. There would be nobody left behind to put out the fires. And the scene would be duplicated a thousand times over before the sun went down. And the next day there would be the final, terrible tempest when the Thuscans arrived. When humanity would go out in a short, confused struggle. There was nothing left to do but prepare to die.... Then he thought again of Avis and knew there was one last, forlorn chance.