Lawyer Ian Mitchell is brought into a deadly game when he receives a box that contains a gun and a picture of a stranger. Along with those items, the box includes instructions for Mitchell to kill the pictured individual. After being attacked by another stranger, Mitchell discovers he has been chosen to take part in the lethal contest by a mysterious organization known as The Watchers, a group he must outwit in order to survive and have any chance to return to his previously normal life with his family.