Michael Harding (Penn Badgley) returns home from military school to find his mother Susan (Sela Ward), happily in love with a man known as David Harris (Dylan Walsh). He seems like the perfect father and husband to everyone; except Michael, who suspects that he isn't quite the man he seems to be.[2]



Along with his girlfriend Kelly (Amber Heard), his father Jay (Jon Tenney), and Susan’s friends (Paige Turco and Sherry Stringfield), they slowly start to piece together the mystery of the man who is set to become his stepfather, but they may be too late in getting to the truth. As people who realize of the inadequacies of David's story start mysteriously dying or disappear systematically, Michael is convinced his soon-to-be stepfather is behind them. After finding his father's body in the basement, Michael sets to save his family and girlfriend before they become David's latest victims.



In the end of their fight, David pulls Michael off the roof of their house and both are left unconscious. After being in a coma for a month Michael finds out from his girlfriend and his mom that David escaped when the police showed up. The scene switches to The Stepfather working in a different area with a different name and he ends up meeting another woman with children.