This book begins with Jake Epping, a thirty-five-year-old English teacher in Lisbon Falls, Maine, who makes extra money teaching GED classes. He asks his students to write about an event that changed their lives, and one essay blows him away—a gruesome, harrowing story about the night more than fifty years ago when Harry Dunning’s father came home and killed his mother, his sister, and his brother with a sledgehammer. Reading the essay is a watershed moment for Jake, his life—like Harry’s, like America’s in 1963—turning on a dime. Not much later his friend Al, who owns the local diner, divulges a secret: his storeroom is a portal to the past, a particular day in 1958. And Al enlists Jake to take over the mission that has become his obsession—to prevent the Kennedy assassination.