The night after the events of previous film paramedics clean up the remains left by psychopathic killer Jason Voorhees and deliver him to the county morgue, where the mortician Axel fails to notice signs that Jason is breathing. After escaping cold storage, Jason slices Axel’s neck with a hacksaw and stabs nurse Robbie with a scalpel.
The next day a group of teens (Paul, his girlfriend Sam, Sarah, her crush Doug, Jimmy and Ted) encounter a hitchhiker while looking for a cabin they have rented for the weekend. The hitchhiker is killed shortly after by Jason, who has returned to the area. The teens find the cabin finally and meet neighbors Trish Jarvis, her brother Tommy, and their dog Gordon. While going for a walk the next day, they meet two local girls, twins Tina and Terri, and they decide to go skinny dipping with them. Trish and Tommy happen upon the scene and before they leave, Trish is invited to a party to take place that night. Afterward, their car breaks down and Trish and Tommy meet a backpacker named Rob, who claims to be hunting for bear in the area. They take him to their house where Tommy shows Rob several monster masks he made himself before Rob leaves to go camping. At the party that night Tina makes a move on Paul, which makes Sam jealous and she leaves for a swim, but Sam is stabbed through a rubber raft. Feeling guilty, Paul goes after Sam to make up and discovers her body just before is stabbed in the groin with a harpoon gun.
Terri rejects Teddy’s advances and wants to leave, but Tina moves onto Jimmy and the two go upstairs to have sex. Frustrated, Terri leaves but she is killed with a spear. At the Jarvis house, Mrs. Jarvis returns home to find the power out, and when she goes out to investigate, she is startled before being killed. Teddy finds an old stag film and brings it up on the projector while Sarah hints to Doug that she wants to have sex with him, and they go upstairs. Jimmy comes downstairs and settles a “dead fuck” status with Ted who had earlier said he can’t satisfy a girl in bed and goes to get a glass of wine to celebrate. Jason appears, jams Jimmy’s hand with a corkscrewand slams a cleaver into his face. Upstairs, Tina notices Terri’s bike is still there before she is grabbed through the window and thrown to her death on top of the teens’ car. Proceeding downstairs, Jason stabs Ted in the back of the head with a kitchen knife through the projector screen. Jason moves upstairs, crushing Doug’s skull in the shower. When Sarah returns and finds him dead she tries to flee the house, but she is killed with an ax to the chest. Meanwhile, Trish and Tommy return from town and discover the power outage. Trish decides to go look for their mother, and orders Tommy to fix the lights. Trish comes across the campsite of Rob, who is convinced that Jason is still alive, which worries Trish and they return to the house. Running next door, they discover the bodies of the teens and Rob is caught and killed by Jason as Trish runs home. They barricade the house, but Jason breaks in and chases them into Tommy’s room. Trish lures Jason out of the house while Tommy escapes. She runs through the teens’ house, then out the upstairs window when he corners her. Returning to her own home she is devastated to learn that Tommy is still there. She senses Jason behind her and tries to kill him with a machete but she misses and he attacks her.
Tommy, having disguised himself to look like Jason as a child, distracts him long enough for Trish to swing the machete at Jason, but she misses. As Jason turns back Tommy takes the machete and jams it in the side of Jason’s skull and he collapses to the floor. The siblings embrace, but Tommy notices Jason’s fingers twitching and he takes the machete and begins to hack at his body, screaming “Die! Die!” while Trish screams his name.
At the hospital, Trish insists on seeing her brother, who was traumatized by the events. He rushes in and hugs her, but gives a disturbed look while staring into the camera, and the screen fades to white.