Potential spoilers ahead!
After obsessed teacher Mr. Fenton (Johnathon Schaech) kills her family and is thrown into a mental institution, Donna (Brittany Snow) moves in with her aunt and uncle halfway across the country. Three years later, Fenton breaks out of the asylum and finds his way back to Donna as she prepares for prom. He infiltrates the hotel in which the prom is being held and kills her friends one by one as he tries to get some "alone time" with Donna. She escapes Fenton at the hotel, but he tracks her to her new home, where he grabs her in a closet. She manages to jump out of the closet, and when he follows, police detective Winn (Idris Elba) shoots him dead.