At Doddsville County High School, the scene unfolds with Carol, portrayed by Caroline Munro, gleefully leading geeky Marty, played by Simon Scuddamore, down the corridor. Their laughter fills the air as they head toward the girls' locker room, completely unaware that a group of students is trailing behind them. As Marty steps into a shower stall and removes his clothes, Carol slyly lets the crowd into the locker room. The curtain is abruptly pulled aside, and chants of "April Fools!" echo as they mercilessly jeer at the shocked, half-naked Marty. The coach strides in, ordering everyone but Marty to head to the gym to "suit up."
Amidst the turmoil, Stella, played by Donna Yeager, expresses her frustration, blaming Marty for their collective punishment. As Carl, portrayed by John Segal, and Ted, played by Michael Saffran, stop by Marty's locker and offer him a joint to ease the situation, Marty decides to indulge while alone in chemistry class. However, the experience goes awry as he quickly becomes ill, prompting him to rush to the locker room.
In a separate incident, Skip, played by Carmine Iannaccone, throws a brick through a window, falsely claiming it came from outside to evade the coach's wrath. Meanwhile, he concocts a dangerous mixture in the chemistry room, leading to a catastrophic fire that injures Marty in the chaos. As he is wheeled out on a stretcher, Carol attempts to apologize but gets startled awake.
Fast forward ten years, and Carol is now a successful actress when she receives a call from her agent, Manny, urging her to consider another film. During a visit from Susan, played by Sally Cross, Carol learns about her engagement and the upcoming class reunion.
On the brink of April 1, Skip embarks on a drive through the countryside and picks up Nancy, portrayed by Kelly Baker, another former classmate. After their vehicle breaks down, former classmates Joe, played by Gary Martin, and Stella come to their aid, towing Skip's car to the abandoned school. As the group arrives at the deserted building, night descends, leaving them to navigate the eerie halls. They venture deeper into the school, discovering remnants of their past, including Marty's old locker, which contains a rat scuttling about. They stumble upon old photographs and a yearbook, reminiscing about Marty's six months of recovery after the accident.
Unbeknownst to them, a sinister figure wearing a jester's mask lurks in the shadows. The group partakes in marijuana, and Carol flaunts her chic cocaine, while Nancy heads to the bathroom with Carol for some privacy. Their moment is cut short by the antics of Skip and Frank, leading to an encounter with Digby, the elderly janitor. He unwittingly warns the group of the school's impending demolition, but lets them explore one last time. However, the masked figure takes a dark turn, confronting Digby and violently silencing him.
The atmosphere quickly shifts when Nancy plays a prank on Skip, pouring a drink down his pants, and Ted's demonstration turns disastrous as he collapses after ingesting a lethal substance, his injuries leading to chaos and panic. Amid the chaos, Carl seizes Carol's keys, but his bid for escape ends tragically when the jester-masked killer ambushes him.
As Shirley heads to the locker room for a wash, she falls victim to a horrific mix-up, facing a gruesome demise in a tub filled with acid. Amidst the devastation, realization dawns on Carol as she screams, "Marty's come back!" Susan arrives, unaware of the carnage inside, and slips into danger herself.
Frantic survivors plan their escape, attempting to access an old tractor while secrets of betrayal and blame unravel among friends. In a chilling moment, Nancy discovers Joe's demise and rushes to inform Carol and Skip. Tension rises as the killer continues to hunt, seemingly unstoppable.
As the dawn approaches, fear settles over the remaining survivors, and Carol deduces that they might only have until noon to confront their haunted pasts. With tensions running high, they must work together to fend off the terrifying force that is coming for them.
The climax crescendos with a vicious confrontation, leading to a stunning revelation that intertwines both dreams and reality, plunging Marty into a cycle of vengeance. In a shocking twist, Marty awakens in a hospital bed, bandaged and disoriented, only to discover that the reunion nightmare was merely a twisted fantasy. Yet the horrors of his past fuel a thirst for revenge, as he dons a nurse's disguise and escapes his confines, desperate to seek retribution against those who wronged him.
