Slumber Party Massacre III

A group of friends play volleyball on a beach in Venice, California. Jackie, one of the group, is a high school senior throwing a slumber party that night, as her parents are out of town looking for a new house. When the friends leave the beach, one of the girls, Sarah, gets into her car and is brutally murdered by an unseen assailant, The Beach Weirdo, in the backseat with a power drill. Jackie returns to her home, and finds her odd neighbor, Morgan, there, wanting to tour the inside of the house; he tells Jackie he is considering purchasing the property when she and her family move.

That night, Jackie\'s friends, Diane, Maria, Juliette, Janine, and Susie, arrive for the party. Shortly after, three boys, Frank, Tom and Michael, arrive and scare them. Jackie angrily tells the guys to leave. Frank and Tom go get something for the girls while Michael goes to apologize to them. Michael encounters a masked killer, who impales him with a \"house for sale\" sign post. After another boy, Duncan, bribes a pizza delivery girl into delivering the pizzas to the girls, she is chased and murdered by the same killer. The girls let Frank and Tom in the house, and Ken, Juliette\'s love interest, appears right behind them.

Upstairs, after Juliette and Ken have sex, Ken leaves and Juliette is electrocuted by an unseen assailant in the bathtub. Soon after, Maria finds Juliette\'s corpse in a closet. As Ken and Tom run to find help, they stop by a lumberyard to get weapons. Ken, revealing himself as the killer, proceeds to whack Tom with a sledgehammer, before slicing into his legs with a chainsaw. Ken goes to a van parked on the street where he has kept the bodies and a giant power drill. Inside, he examines a newspaper clipping regarding the suicide of his police officer uncle Billy, and recalls how he was sexually abused by him.

Back at the house, Ken barges in and kills both Duncan and Frank. Maria finds Tom\'s dead body before her and Janine run to the door but Ken follows and Maria flees. Janine jumps through the glass door and Ken drills her in the back, killing her. Susie hides in an upstairs closet, but Ken attacks her and knocks her unconscious. Before he can kill her, Maria knocks him in the head with a lamp and he chases her, Jackie, and Diane into the basement, where Jackie uses a spear gun to shoot him and they run back upstairs. Susie regains consciousness, and throws bleach in Ken\'s face, blinding him. He catches Maria and kills her as well. Jackie, Susie and Diane manage to knock Ken unconscious with a croquet mallet.

As the three contemplate what to do, Ken awakens and begins slashing Diane with a knife, killing her. Susie manages to pin Ken to the floor long enough for Jackie to viciously plunge the drill through his chest multiple times. After he dies, Jackie finds a photo in Ken\'s shirt pocket of him as a child with his uncle. Susie goes to answer the police knocking on the door and the credits roll.