While driving home from a day at graduate school, Kevin receives a call from a mysterious stranger who calls himself Slater. Slater demands Kevin confess his sin in the next three minutes or the vehicle he is manning will be blown to pieces.
Thus starts a harrowing chain of events. After narrowly escaping his exploding car, Kevin continues to receive phone calls from Slater, each with another riddle, another consequence, and another three minutes to confess his sin.
The problem is Kevin is unsure of what that sin might be. And Slater's cycle won't stop until he figures it out.