When Captain Colter Stevens wakes up in the body of an unknown man, he discovers he's part of a mission to find the bomber of a Chicago commuter train. He is part of a government experiment called Source Code, a program that enables him to cross into another man's identity in the last 8 minutes of his life. With a much larger target threatening to kill millions, Colter re-lives the incident over and over again, gathering clues, until he can solve the mystery of who is behind the bombs.