The novel centers on Jackson Oz, who is an outcast among professional and academic ecologists and biologists. Oz has tried for years to get these scientists to listen to the data he has been collecting on the increasing numbers of mammal attacks on humans. He becomes so obsessed with this goal that he quits graduate school and devotes himself to full-time data collection and arguing his case. Finally, on a trip to Botswana, he survives an attack by a large band of male lions in which about 100 people are killed over a large area. He saves the life of ecologist Chloe Tousignant, and together they seek to warn the world that something has caused mammals of all types to band together in what seems to be an orchestrated effort to eliminate humans. The balance of the novel sees Oz gaining acceptance of his data, while world leaders take misguided actions to solve the problem, only to see even worse mammal attacks threaten the existence of man.