Following Jason's rampage at Crystal Lake, his lifeless body is taken to the local morgue while the authorities clean up the scene. Also brought to the hospital is the sole survivor, Christine. In the morgue, the morgue attendant Alex begins to have sex with a nurse, who becomes enraged when he prematurely ejaculates. After she storms off, Axel grumbles to himself while trying to get dressed and fails to notice that Jason is missing. Suddenly, the killer appears behind him and murders with a surgical tool. He then follows the nurse, who is attending to Christine, and slays them both.
Meanwhile back at Crystal Lake, we meet the Jarvis family, consisting of Ms. Barbara Jarvis, her daughter Amanda and son Tommy. Their idyllic life is shattered by the arrival of a gang of horny teenagers, who have rented out the neighbouring house for a weekend of partying. The group consists of Jimmy, Ted, Doug, Bill, Sam and Sara.
The group meets the Jarvis family and two local twins, Tina and Tanya, as well as a drifter named Rob who assists them when their car breaks down. That night, Tommy watches Sam and Bill having sex from his bedroom.
The next night, the party begins. The twins arrive and Tanya begins to dance with Bill, making Sam jealous. She storms off to go skinny dipping but is killed by Jason. Bill follows her and is also killed. Jimmy dances with Tina, making Tanya jealous so she decides to leave in spite of heavy rain, but Jason murders her just outside the house. barbara is outside watering her plants and witnesses tanya's death and screams. jason then chases her into the woods, trips her with his boot, and then murders her as well.
Doug and Sara go to take a shower together, where Doug takes Sara's virginity. Jimmy and Tina also go upstairs to have sex, leaving Ted alone downstairs. He begins to smoke both and hooks up a large projector and begins to screen porn for himself. Jimmy comes downstairs to brag and get some beer, while Ted passes out in his armchair. Jimmy shouts to Ted asking for the corkscrew, when Jason appears and uses the corkscrew to stab Jimmy through the eye. He goes back Upstairs and plunges his machete through Tina, killing her. then he goes back downstairs and smashes ted's head in the projector screen.
Sara gets out of the shower and goes to get ready to continue having sex with Doug in the bedroom. However, when Doug does not follow, she goes into the bathroom and finds that Jason has gutted Doug and his hung his body from the shower head. He then attacks Sara and pulls her towel off. She runs outside, naked, and tries to get into the car when Jason drops Tina's body on top of it and jumps on top of her and decapitates her with an axe.
Meanwhile, Tommy falls asleep and Amanda meets Rob at his tent in the woods. He explains that his sister, Becca (from the second film), was murdered by Jason and he is hunting for him, and believes that he is alive and active in the area. They return to the house and Amanda is horrified to find her mother's corpse lying the bath tun upstairs. She gets Tommy while Rob goes over to the other house to find Jason. Amanda follows and witnesses Jason tackling Rob before he chases her through the house. She escapes and her and Tommy board up their house, but Jason throws Rob's body through the window and kicks the door down. Tommy, hiding upstairs, cuts his hair off, remembering the stories of Jason's childhood and making himself look like Jason when he was a child. He comes downstairs and distracts Jason, saving Amanda. Amanda then attacks Jason, knocking his mask off. He turns to her but Tommy attacks him, enraging him even further. Jason grabs Tommy and begins to violently choke him. Amanda picks up Jason's machete and splits his head open, finally killing him. She and Tommy then share an embrace.
Michael Bailey Smith - Jason Voorhees
Dee Wallace - Pamela Voorhees
Scout Taylor Compton - Amanda Jarvis
Jamie Lee Curtis - Barbara Jarvis
Kat Dennings - Samantha
Beth Behrs - Sara
Topher Grace - Alex
Jaime King - Nurse Morgan
Chelan Simmons - Christine
Emma Bell - Alice (Flashbacks)
Amanda Seyfried - Ginny (Flashbacks)
Axel - Stabbed with surgical tools
Nurse Morgan - Stabbed with surgical tools
Christine - Stabbed with surgical tools
Sam - Drowned
Bill - Stabbed with rusty pole
Tanya - Sliced with machete
Mrs. Barbara Jarvis- body slashed several times with meat cleaver
Jimmy - Stabbed through eye with corkscrew
Tina - Impaled with machete and thrown through window
Ted- head smashed into projector
Doug - Gutted
Sara - Decapitated with axe
Rob - Stabbed
Jason Voorhees - Head split open with machete
this film was such a success, one more friday the 13th film is in development, titled friday the 13th 5: blood-way house, about tommy jarvis, now a colledge student, is so mentally traumatized by the murders of the fourth film, he is sent to a half-way house to recover along with other teens. but soon, jason returns from the dead and starts killing everyone.