Two months later after Crystal Lake's brutal massacre, Alice (Adrienne King), wakes up after dreaming about Mrs. Voorhees' decapitation. She talks on the phone to her mother, then she takes a shower and decides to boil the kettle. When she opens the fridge, she finds Mrs Voorhees' severed head, before being stabbed in the head with an ice pick by a unidentified assailant.

Five years later, a group of young adults have come to Crystal Lake to attend a counselor training center that has been set up near the now-condemned Camp Crystal Lake. While some counselors, named Jeff (Bill Randolph) and Sandra (Marta Kober), are in town on their way to the facility, the town drunkard Crazy Ralph (Walt Gorney) appears and tells the counselors to turn back, as the young counselors five years ago did not heed his warning. At the camp, Paul (John Furey), the leader of the group, explains how camp counseling is a serious job, and that the main danger in this area is bears. Ginny (Amy Steel), Paul's former girlfriend, arrives in her broken-down Volkswagon and attends the meeting as well.

One night, around a campfire, Paul tells the people about how Jason Voorhees drowned in the same lake which their training area also bounds; how his mother was found to be the infamous murderer of "Camp Blood"; and that Alice survived only to disappear shortly thereafter, and that some of the local residents believe Jason is still alive and viciously protects the area around Crystal Lake. When the counselors seem into the story, they are shocked by a mask-wearing man with a spear, but it only turns out to be the prankster Ted (Stu Charno) in a monster mask and Paul claims that Jason is dead. While some of the counselors are seen making out, Crazy Ralph is standing behind a tree, and is suddenly killed using a garotte around his neck.

The next day, Jeff and Sandra sneak away to Camp Crystal Lake, which is now in disrepair. As they are about to go into one of the cabins, they are stalked by an unseen man who then approaches them; but it is revealed that is a local policeman (Jack Marks) who has caught them trespassing. The policeman returns the two counselors to camp, where Paul only recommends a light punishment. However, when driving away, the policeman sees somone dart out in front of his squad car, and is running in the direction of the off-limits Camp Crystal Lake. The policeman chases after the masked man to arrest him as well, only to lose him and go into a cabin. The policeman then sees a horrifying sight (not shown to the viewer) before having a claw hammer slammed into the back of his head.

After getting to know one another and participating in some training exercises (which consist of dancing, jogging through the woods, swimming and a cookout), the majority of the trainees leave the campsite to party in town for the evening with the exception of Jeff, Sandra (it is their punishment), Mark (Tom McBride) (he is in a wheelchair), Vicki (Lauren-Marie Taylor) (she wants to stay and talk to Mark), as well as Vicki's friend Teri (Kirsten Baker), and Scott (Russell Todd).

Teri decides to go for a swim, and goes skinny dipping. During this, her clothes are stolen by someone, and she exits the lake. It is revealed to be Scott who stole her clothes. As they playfully fight, Scott is caught in a trap, and is hung upside down. Teri goes to look for something to cut him down with. While she is looking, Scott's throat is cut by the assailant, using a panga machete. When Teri returns, she thinks Scott is playing a game, but finds him dead, and she is killed off-screen.

Meanwhile, far away from the camp, the other group of counselors are partying at a local bar. Ginny brings up the legend of Jason, imagining what Jason would be like if he were alive, deducing he had seen his mother murdered and would be a vengeful creature unaware of the meaning of life and death. Paul, in response, dismisses her concerns and tells her that he is only a legend since Jason drowned in the lake and his demented mother, whom murdered seven people at Camp Crystal Lake, is also dead and buried. Ginny gets bored and decides to return to the camp, and Paul accompanys her, while Ted and the rest of the counselors stay behind at the bar.

As it begins to rain, Vicki goes to put some make up on, so Mark will find her more attractive. Mark is on the balcony, when the killer attacks him from behind, by slamming the machete through his head and his corpse, along with his wheelchair falls down the raining stairs. Vicki goes into the house to look for Mark, but cannot find him. Jeff and Sandra are upstairs having sex, but not knowing the assailant heads upstairs and resulting both of them impaled through the bed with a spear. Vicki goes upstairs, and finds them dead, and finds the assailant, wearing a one-eyehole gunny sack over his head, where then she is stabbed through her stomach with a chef's knife.

Upon their return to camp, the rain lets up and Ginny and Paul discover the lights are not working in the main cabin and sheets on an upstairs bed appear to be covered in blood. During the search, Ginny finds the two bodies of one the counselors, and then opens the freezer, where Crazy Ralph's corpse falls out. Soon, Paul is attacked by the gunny-masked assailant as Ginny runs out into the woods.

After a lengthy chase, Ginny stumbles upon the assailant's cabin and enters. In the back room, she discovers an altar with Pamela Voorhees' head (Now mummified) on it, surrounded by the bodies of the recent victims. At this point, Ginny realizes that Jason Voorhees is the murderer, who seemingly survived his drowning and now seeking revenge upon his deceased mother. Using her study of child psychology to her advantage, Ginny dons Mrs. Voorhees' sweater and deceives Jason into believing that she is his mother (although Jason wises up when he sees his mother's severed head). Jason sees Ginny attempting to attack him with his mother's machete, in which he quickly acts by slashing Ginny's right leg with a pickaxe. Paul, (still alive) runs in and tackles Jason to the floor, at which one point Jason overthrows him and prepares to kill him with his pickaxe. Ginny revives, takes the machete, and slams it through Jason's left shoulder, seemingly killing him. Afterwards, Ginny and Paul uncover his disfigured face (unseen to the viewer) as they leave the cabin.

Paul and Ginny retreat back to their cabin, now believing Jason is dead and find Muffin, Terri's pet dog (alive and active). As Ginny calls to her dog Muffin to come, an unmasked and deformed Jason (Warrington Gillette) breaks through the window (With the machete still intact in his shoulder) and pulls Ginny out.

The next morning, Ginny wakes up while being placed in an ambulance with no recollection of what happened to Paul. The final shot shows Mrs. Voorhees' head still on the altar, where Jason is also nowhere found, but it is strongly implied that he is still active, before ultimately fading to black.