When former U.N. investigator Gerry Lane (Brad Pitt) and his family get stuck in urban gridlock, he senses that it's no ordinary traffic jam. His suspicions are confirmed when, suddenly, the city erupts into chaos. A lethal virus, spread through a single bite, is turning healthy people into something vicious, unthinking, and feral. As the pandemic threatens to consume humanity, Gerry leads a worldwide search to find the source of the infection and, with luck, a way to halt its spread.