Trish Devereaux-Craven, an 18-year-old high school senior, decides to throw a slumber party while her parents are away for the weekend. Their neighbor, David Contant, is given the job of checking in on the girls during the night. She awakes to the sound of her radio and gets dressed shortly before going to school. Meanwhile, Russ Thorn, an escaped mass murderer with a preference for power drills, kills a telephone repair woman and steals her van. Trish meets up with her friends Kim, Jackie, and Diane, the girls on her basketball team. A new girl, Valerie Bates, is invited by Trish, but refuses after hearing Diane talking cruelly about her. Russ watches the girls leave school from the van and a girl, Linda, goes back inside the school to retrieve a book for a test, only to be locked inside and attacked by Russ, who injures her left arm. She eventually hides in the shower room, but the killer finds out where she is because of her blood loss, and kills her before escaping to the van.