From Boston to San Diego, it was the same in every city. Thicker than air, the odorless, invisible gas poured from vents, oozed across tile and carpet alike, and escaped out onto the sidewalks and streets. Children and elderly were the first to slip into unconsciousness, but men and women of all ages joined them before too long. Some dropped with sickly, bloody crunches. Others merely slid down walls as if they had fallen asleep. Hundreds of thousands died within minutes. By the time anyone realized what had happened, it was already too late. The attack was over. The war had begun. This is the story of how it ended.