When decorated soldier 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. In an assignment unlike any he's ever known, he learns he's part of a government experiment called the "Source Code," a program that enables him to cross over into another man's identity in the last 8 minutes of his life. With a second, much larger target threatening to kill millions in downtown Chicago, Colter re-lives the incident over and over again, gathering clues each time, until he can solve the mystery of who is behind the bombs and prevent the next attack.