In the summer of 1958, two camp counselors, Barry and Claudette, sneak away from a campfire to have sex. An unknown assailant follows them and is recognized before brutally attacking and killing them.
Twenty-one years later, Annie arrives at the town of Crystal Lake asking for a ride out to the camp. Despite warnings from the town crazy, Ralph, about “camp blood”, a truck driver gives her a ride. On the way he too warns her of a death curse supposedly on the camp after a drowning in 1957, two murders in 1958, and several non-fatal incidents following that. She heeds his warning but cannot back out. He drops her off halfway to the camp, and she finds a ride in a Jeep. She becomes panicked when the unspeaking driver drives past the camp’s entrance and she tries to flee, but the driver surprises her in the forest and slashes her throat. Meanwhile, three new counselors, Marcie, Ned, and Jack, arrive at the camp and meet the camp’s owner, Steve Christy, two of his hands, Bill and Alice, and another counselor, Brenda. After setting them up, Steve leaves for supplies. The sheriff arrives shortly after, looking for Crazy Ralph, who appears shortly after he leaves, disturbing them by proclaiming they are “all doomed” before leaving.
As a storm rolls in, Ned spots someone in one of the cabins and investigates. Meanwhile, Marcie tells Jack about a recurring dream of rain turning into blood. As the storm moves in on them, they go to a nearby cabin to have sex, unaware that Ned is in the upper bunk, dead from a slashed throat. After Marcie leaves the cabin to wash up, Jack is impaled in bed, and someone kills Marcie in the bathroom with an axe. Bill, Alice, and Brenda are playing strip Monopoly when Brenda realizes her cabin windows are open and returns to her cabin. Once there, she hears what sounds like a child calling for help and is lured out onto thearchery range where she is killed. At the main cabin, Alice hears Brenda’s screams; she and Bill go searching for their friends, but, discovering the axe in a bunk, are left with more questions than answers. Bill convinces Alice that it is a prank, and they return to the cabin. Meanwhile, Steve returns to the camp on foot and recognizes someone at the entrance before being stabbed and killed. The attacker then turns off the generator, and Bill leaves alone to fix it.
Alice awakens sometime later and goes searching for Bill, only to find his body pinned to the generator room door by arrows. She flees back to the main cabin, and Brenda’s body is hurled through the window from outside. A jeep pulls up and Alice runs out for help, encountering a woman named Mrs. Voorhees, an “old friend of the Christy family.” Mrs. Voorhees sees Brenda’s body and recalls losing her own son Jason, who drowned in 1957 because the counselors watching him were having sex and not paying attention. She then grows unstable and pulls a bowie knife on Alice and attacks her with it. Alice bludgeons her with a fireplace poker and runs out of the cabin, discovering Annie and Steve’s bodies as she flees. Mrs. Voorhees finds her again, and again Alice escapes, eventually hitting Voorhees with a frying pan, so hard that this time she believes she is dead. By the lake Mrs. Voorhees attacks Alice again with a machete. After a violent battle on the beach, Alice gains control and decapitates her attacker. Stricken with shock, Alice then pushes a canoe out onto the lake and falls asleep in it.
The next morning, police investigating see Alice on the lake and call to her. Suddenly, the decomposing body of Jason leaps from the lake, dragging her under the water. She wakes in the hospital, having recalled the murders and the boy in the lake, but the sheriff claims they did not find any boy. After a pause of confusion she then proclaims that “he’s still there” before the camera returns to the lake, now at peace.