Plot

At a high-school senior prom, a masked killer stalks four teenagers who were responsible for the accidental death of a classmate six years previously.

For six long years, Hamilton High School seniors Kelly Lynch, Jude Cunningham, Wendy Richards, and Nick McBride have been hiding the truth of what happened to 10-year-old Robin Hammond the day her broken body was discovered near an abandoned convent. The foursome keep secret how they backed Robin into a corner until, frightened, she stood on a window ledge and fell to her death. Though it was an accident, the then-12-year-olds feared they would be held responsible and vowed to never tell. But someone else was there that day--watching--and that someone is now ready to exact murderous revenge on prom night.

Six years ago, when young Robin Hammond crashed through a broken window, her playmates vowed to keep the accident a secret. They promised that no one would ever know, but someone already does. Now, after years of keeping the secret, Robin's sister Kim is about to be crowned prom queen, but a chilling event undermines her party plans. Revenge for the six-year-old murder is around the corner as the unknown observer turns maniacal killer stalking the high-school halls. Kim's friends are disappearing and the dark, empty halls are filling with blood. This was the senior prom where some were crowned and others lost their heads.

In 1974 Cleveland, the kids Wendy, Judy, Kelly, and Nick are playing hide-and-seek in a derelict building. While going to school, siblings Kim, Alex, and Robin stop near the building since Kim needs to return home. Robin flees from Alex and runs to the building, and the quartet frightens her and she falls off the window, immediately dying. They promise to each other to keep secret about what have just happened to Robin. Six years later, on the prom night, serial killer Leonard Murch, who is suspected of murdering Robin, escapes from the mental institution where he is interned and the police is afraid that he returns to town to seek revenge. When Murch is captured by the police in another town, Lt. McBride feels relieved and resolve to enjoy the prom. However, a killer is beginning a crime spree in Hamilton High School.—Claudio Carvalho, Rio de Janeiro, Brazil

Years earlier, Wendy, Kelly, Nick, and Judy played a hide-and-seek game called "Killer Is Coming" in an abandoned building. Robin, a younger girl desperate to be friends with them, tries to join in, but accidentally causes Nick to be found. The four of them chase, tease, and trap Robin, causing her to climb up backwards by a window, which she falls out to her death. The four of them swear to secrecy, but someone knows the truth. On their prom night, they are stalked at by a mysterious killer who is seeking retribution for Robin's years earlier.—charmardee-smith

Inside an old abandoned building, four children are playing a game in which they all hide while one of them looks for the others, calling out "the killer is coming!" Young Kim and her two twin siblings, Alex and Robin, walk by and see the children playing. Kim and Alex leave, but Robin lingers, hoping to join the game. But upon entering the building, the four kids gang up on her, chanting "kill!" until Robin has nowhere to go. Backing up into a window, Robin crashes through and falls out of a second floor to her death below. One of the kids, Nick, wants to get help, but Wendy convinces all of them that the best thing to do is tell no one and never tell anyone about what happened. Wendy, Nick, Jude, and Kelly swear to keep quiet. As they leave the building and ride away on their bicycles, an unseen person sees them ride off. Later that evening, Robin's father, Mr. Hammond (Leslie Nielsen) and the police are at the scene. They have surmised that Robin was the victim of a sexual attack by a homicidal maniac. They think they know who is responsible and the cops go off to question a suspect.

Six years later.

The now grown-up Kim (Jamie Lee Curtis) and Alex (Michael Tough) are visiting their sister's grave with their parents. A little later, an unseen person with a creaky voice is telephoning each member of the guilty party one by one telling them, "I'll see you at the prom!" The timid Kelly is upset, while Jude and Wendy think that it's a prank.

Meanwhile, Nick's father, Detective McBride (George Touliatos), is unsettled because a psycho killer named Leonard Murch has escaped from a local clinic hospital. Murch was an ex-convict and known sex offender/pedophile who the police (mistakenly) suspected was responsible for Robin's death. That night when McBride and his men approached Murch at his apartment for questioning, he climbed out a back window of his apartment and fled before they could ask him any questions. Murch led the police on a high speed car chase through the town which ended when his car slid off the road resulting in it getting wrecked and exploding in a mass of flames. Murch suffered horrible burns all over his body and has been residing in the asylum for the criminal insane after he was deemed mentally unfit to stand trial for Robin's murder. McBride suspects that Murch may want to head back to the town where it happened to look for more victims. When the police discover the dead body of a nurse that Murch took as a hostage during his escape from the hospital, McBride and the asylum psychiatrist Dr. Fairchild believe that Murch may have returned to the town for revenge against everyone.

In town, it is revealed that Nick is Kim's latest boyfriend. Wendy is Nick's ex-girlfriend, and she is certainly not happy that the new couple are going to their senior prom together. Wendy tries to assure Kim that the relationship will not last by telling her "It's not who you go with. It's who takes you home". Later, the school bully and misfit Lou (David Mucci), is messing with Kim in the cafeteria wearing a mouth-less ski mask. Alex steps in to defend his sister, and he holds his own against Lou's two pals until Lou sucker punches him in the back. Brought before the principal, whom is Mr. Hammond, he suspends Lou for fighting. As Lou leaves the school grounds, Wendy tries to talk to him. When Nick and Kim are walking around, Nick tries to tell her about that fateful day, but is he not able to.

Meanwhile, Wendy makes devious plans to break up Kim and Nick, and she tells Lou that she doesn't want anyone hurt. Lou tells her that he will take care of it. Nearby, Jude is picked up for a ride home by Slick, an outcast student who drives a Chevy van, whom he asks her to the prom and she accepts. In the girls locker room after tennis practice, Wendy finds her school photograph torn from the yearbook and hanging on the front of her locker. When Kim and her friend, Kelly, are alone, they hear a loud noise in the locker room and they see that a mirror has been smashed. After checking around the locker room, the return to see that a fragment of the mirror is gone. Jude and Kelly both find their yearbook photographs inside their lockers, as does Nick.

That night, Lou picks up Wendy to take her to the prom. Mr. Hammond is the chaperone and Alex is the DJ for the disco music. Everyone is having a good time dancing and listening to the music and watch Kim and Nick do their well-choreographed dance on the dance floor before everyone. Detective McBride secretly arrives at the dance to oversee it and to make sure that nothing bad happens.

Kelly and her boyfriend, Drew, leave the gymnasium for a part of the school in a locker room where they begin to make out. Kelly decides that she cannot go any further, and an irate Drew goes elsewhere telling Kelly that he knows "plenty who will". After Drew walks out on Kelly, an unidentified figure donning the ski mask and wearing all-black clothing stealthily approaches the tearful Kelly and kills her by slitting her throat with a mirror shard.

Jude and Slick decide to sneak out of the festivities in the gym for some intimate time as well. Outside, Jude and Slick are in the back of his van enjoying the privacy. After spending a bit of time outside the van, they hear noises and thinking that someone is nearby spying on them, go back inside the vehicle to smoke some marijuana. After a minute, the back doors open and the masked killer stabs Jude's neck with the mirror shard. The murderer then leaps in after Slick who fights back and pushes the killer out of his van and starts it up to run the killer over. The killer leaps out of the way and grabs onto Slick as he is trying to drive away. After wildly spinning around, the killer jumps free and the van with Slick inside goes over a cliff and explodes.

The killer returns to the school, now wielding a felling axe and follows Wendy out of the gym to the ladies room where she is putting on makeup. The lights are turned off and the killer attacks her. Wendy gets away and a long chase through the school begins as Wendy tries to outrun her axe-wielding pursuer. The chase leads through the darkened halls, classrooms, and the workshop area. Wendy almost gets away, but in due time the killer finds her when she screams to the discovery of Kelly's body in a linen closet and she is axed to her death.

Back inside the prom, McBride is told by another police officer that Murch has been caught and was several miles away from the town. The alcoholic school janitor, Sykes, having just witnessed Wendy's murder, attempts to notify the school staff, but they dismiss it as a drunken rant.

Kim begins looking for her father, but cannot find him as he is to announce the new prom king and queen. So, a teacher decides to announce the winners himself. Backstage, Nick and Kim ready themselves for the announcement of prom king and queen when Nick is accosted by Lou's thugs and Lou takes his place backstage with the crown. The killer, believing Lou to be Nick-in-waiting, approaches from behind and decapitates Lou, with his head landing on the catwalk and causing the students to scream and flee from the gymnasium. The killer is knocked out when he accidentally hits a fuse box. Kim finds Nick and frees him and tries to help him get out of the building. The killer revives and, quickly realizing his mistake, blocks the exit and attacks Nick and Kim. (Note: the killer only wants to kill Nick and cares little about Kim whom is trying to stop him.) After a struggle between Nick and the killer, Kim bluntly hits the killer's head with his own axe where Kim pauses for a moment and recognizes the killer's identity from the eyes.

The killer stumbles away and outside where McBride returns with the police who have surrounded the place. As they take aim, Kim runs outside and yells at the officers not to shoot. Kim runs to the collapsed killer's side, who is revealed to be Alex, the twin of Robin. Kim holds Alex who tells her that Nick and his friends were responsible for killing Robin. As Alex dies from his wound, Nick walks outside and stares at a tearful Kim as she continues holding her deceased brother in her arms.