Two months after the Camp Crystal Lake massacre, sole survivor Alice Hardy is recovering from her traumatic experience. In her apartment, she suddenly began having nightmares, but wakes up safe in her bed. Soon after she is startled by a cat, then finds the head of Pamela Voorhees in her refrigerator. She then is murdered by an unseen Jason Voorhees with an ice pick.
Five years later, Paul Holt hosts a camp-counselor training camp at a building near Crystal Lake. Included among the counselor hopefuls are lovers Jeff and Sandra, troublemaker Scott, his girlfriend Terry, wheelchair-bound Mark, sweet-natured Vickie, jokester Ted, and Paul's assistant and girlfriend, Ginny. At the campfire that night, Paul tells them the legend of Jason Voorhees to scare the other counselors from entering Camp Crystal Lake. That night, Crazy Ralph wanders onto the property to warn the kids, but is garroted from behind by Jason. The next day, Jeff and Sandra attempt to go off to Camp Crystal Lake, but find a recently killed animal that looks like Terry's dog, Muffin. They are then discovered trespassing by the sheriff and return to the camp. On the way, the sheriff spots a figure with a sack hood running across the street (who's revealed as Jason), and chases him into the woods, where he comes across a rundown shack. As he investigates, he discovers a sight that horrifies him, moments before he's suddenly killed with a claw hammer to the back of his head.
Back at camp, Paul offers the others one last night on the town, but makes Jeff and Sandra remain behind as punishment for their earlier excursion. Terry stays behind to look for Muffin and Scott stays behind to flirt with Terry. Mark doesn't want to go and Vickie decides to stay with him. Terry goes swimming and Scott plays a prank on her by stealing her clothes. He then gets caught in a rope trap and hangs upside down from a tree. While Terry goes to get a knife to cut him down, Scott's throat is then slashed with a machete and Terry is killed (offscreen) when she returns. At a noisy bar in the nearby town, Ginny muses that if Jason were still alive and witnessed his mother's death, it may have left him with no distinction between life and death, right or wrong. Paul scoffs at the idea, proclaiming that Jason is nothing but an urban legend.
Back at the camp, while Mark is waiting for Vickie, he's killed by Jason with a machete to the head and his wheelchair is pushed down a flight of outdoor stairs. Jason then goes upstairs and kills Jeff and Sandra with a spear as they are having sex. Vickie returns and comes across her friends's bodies, before she is stabbed by Jason. Ginny suspects something is wrong when she and Paul return to find the lights out and the place in disarray. Jason creeps through the dark and attacks Paul before turning on Ginny who screams and runs in terror.
She's then chased through some of the cabins before fleeing into the woods and eventually comes across the old shack. After barricading herself inside, she finds a rough altar with Pamela Voorhees's severed head on it surrounded by a pile of Jason's victims, including the corpse of Alice Hardy. Ginny quickly puts on Pamela's sweater and tries to psychologically convince Jason that she's his mother. The ruse fails when he spots his mother's head on the altar and he attacks Ginny. Paul suddenly intervenes and attacks Jason but is quickly overwhelmed. Just as Jason is about to kill Paul, Ginny picks up a machete and slams it down into his shoulder, seemingly killed him.
Paul and Ginny returns to the cabin and are greeted at the door by Muffin the dog, alive and well. Just as they feel at ease, an unmasked Jason suddenly bursts through the window behind Ginny who grabs to drag her out while she screams, as the screen fades to bright white. She then awakens being loaded into an ambulance and calls out for Paul, who is nowhere to be seen. Meanwhile, back at the shack in the woods, Pamela's head remains on its altar.
How was Mark killed?
machete to the head and his wheelchair is pushed down a flight of outdoor stairs