The film begins with Alice (from the original film) dreaming about killing Mrs Voorhees. 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! After this, she is stabbed in the head with an icepick by a mystery 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 are in town on their way to the facility, Crazy Ralph appears and tells the counselors to turn back, as the young counselors five years ago did not heed his warning. Paul, the leader of the group, explains how camp counseling is a serious job, and that the main danger in this area is bears. 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 man with a spear, but it only turns out to be Ted in a monster mask and Paul claims that Jason is dead. While some of the counselors are seen making out, Crazy Ralph is standing by a window, and is suddenly killed by a prowler using a garotte. 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 who has caught them trespassing. The policeman returns the two counselors to camp, where Paul only recommends a light punishment. However, when driving, the policeman sees a masked man 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. It is not shown to the viewer as the prowler who killed Crazy Ralph also murders the policeman from behind. 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 with the exception of Jeff, Sandra (it is their punishment), Mark (he is in a wheelchair), Vicki (she wants to stay and talk to Mark), Teri, and Scott.
Teri decides to go for a swim, and goes skinny dipping. During this, her clothes are stolen by someone, and she exits the pool. 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 killer. When Teri returns, she thinks Scott is playing a game, but sees he is dead. She is then killed too.
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, and his wheelchair falls into the lake. Vicki goes into the house to look for Mark and can't see him.
Jeff and Sandra are upstairs having sex, when the killer kills them in a double impalement scene. Vicki goes upstairs, and finds them dead, when she is confronted by the killer wearing a pillowcase, and she too is killed.
Upon their return to camp, 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. Ginny screams in horror when she sees the dead bodies of two of the counselors, and then opens the freezer and sees the corpse of Crazy Ralph fall out. Paul is attacked by a figure whose head is covered with a pillow case as Ginny screams and runs out into the dark woods. After a lengthy chase, Ginny stumbles upon a run-down cabin and enters. In the back room, she discovers a table holding the severed head of Pamela Voorhees. Littered around the table are several bodies of the slain trainees as well as the rotten corpse of Alice and the newly murdered policeman. The killer is identified as Jason Voorhees, who seems to have survived his drowning. 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). After Paul wrestles with Jason, she slams a machete through his shoulder. Paul and Ginny retreat back to their cabin believing Jason is dead and find Muffin, Terri's pet dog. As Ginny calls to Muffin to come, an unmasked Jason leaps through the window and begins to pull Ginny out. Ginny wakes up while being placed in an ambulance with no recollection of what happened to Paul.
