Frederik Pohl - Plague of Pythons

In a post-apocalyptic world where every government in the world has been overrun by its own military machinery, only to see that military machinery self-destruct, people are randomly being affected by a plague that seemingly takes over their brains and forces them to commit heinous crimes. Chandler is one of these unfortunate victims, the perpetrator of rape and murder. He is driven out of his community as a Hoaxer (someone who feigns being a victim of the plague), branded on his forehead with the letter H. But he is not feigning. In his travels, he finds the source of the plague, and it's not what people think. It's up to him to deal with it, and he does. But to what end? — Summary by Nick Bulka