When Ben leaps into one of five people in an elevator at a 1962 nuclear reactor, he must figure which one triggers a bomb that kills them all. Each time the bomb goes off, he leaps into another one of them an hour earlier, resetting the scene.

At Princeton University in 1955, Ben must find a formula hidden by Albert Einstein that holds the key to nuclear energy before the Nazis get it. He's surprised to run into a familiar face on campus.

Ben leaps into the body of a 1974 Baltimore firefighter and is unexpectedly reunited with his time-crossed love, Hannah, and her son, Jeffrey. Trapped in an inferno, Ben must save their lives.