Ben lands in 1979 Chicago as Jack Armstrong, a devoted security guard to talented pop singer Carly Farmer. During Carly's prep for a big concert, it quickly becomes clear her life is in danger and Ben must determine who is trying to kill her and why.

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 and the scene resets on a loop.