When the zombie apocalypse begins, Layne is on a plane flying 30,000 feet above the northwestern United States. Recently divorced Evan and Cynthia are at their daughter's ballet recital. Jordan is working as a cashier at a grocery store. Max is at the carnival with his tightly knit family. Ben and Charlotte have just survived a car crash. Zoe is all alone on her way home from school. Martha is at her husband's funeral.

On June 21st, 2013, a random selection of the world's population changes. People who were once friends and family turn into murderous zombies, and people who were once strangers or enemies turn into allies. Seven groups of survivors across America will have to struggle to escape, survive, or learn what caused people to turn into monsters—or else become one of them.