Shriek If You Know What I Did Last Friday the Thirteenth

The Killer attacks Screw Frombehind in her house. She is electrocuted when she crashes into a bug zapper. The killer's mask appears to melt into a Scream-like disguise as he revels in the kill.

The next day, Dawson Deery enrolls at Bulimia Falls High School and meets a new group of friends: Boner, Slab, Barbara, and Martina. He wonders if Martina might be a lesbian, and they discuss Screw's death, trying to feel safe at school. Meanwhile, the surrounding chaos foreshadows danger beyond the classroom.

At the school, they encounter Hagitha Utslay, a flashy reporter who accuses Dawson of being the killer. Barbara's brother Doughy, a bumbling security guard, dismisses Screw's death as a prank. The tension escalates when Hagitha's cameraman is murdered, signaling the danger surrounding them.

As the day continues, the killer's plan expands beyond the school: an anthrax bomb is being built and an assassination attempt on the president is hinted elsewhere. The killer also sends letters to each group member revealing secrets from their past. The revelations confront them with guilt tied to a deer-driving incident and other misdeeds, deepening the sense that danger lurks everywhere.

Dawson receives a letter admitting he was the deer knocked down by the others, wearing a forced costume and salt lick. The hillbilly who coerced him dies in an explosion caused by farting in a fireplace. The bizarre backstory ties into the killer's obsession with exposing secrets.

With danger escalating, the group decides to spend the night in a secluded house and plans to head to Slab's after school. They travel there as the day edges toward evening, hoping to outlast the killer. The plan shifts the tension from school corridors to a remote residence.

Inside Slab's house, the danger continues as the killer corners the friends. In a bizarre turn, Principal Interest confronts the killer and electrocutes himself in a bathtub, ending that encounter unexpectedly. The house becomes a battlefield where fear overrides reason.

Later that night, Boner brings a girl to a bedroom, attempting to lose his virginity, but the killer interrupts. Boner suffers a heart attack during the confrontation. The surrounding chaos leaves the remaining friends scrambling to survive.

Barbara is chased outside by the killer but is saved when an allergic reaction to bee stings complicates the chase. Meanwhile, Slab's steroid abuse triggers a dramatic head explosion, shocking the partygoers. The body count and shock value escalate further.

Martina and Dawson flee from the killer, while Hagitha and Doughy flirt and play strip poker nearby instead of helping. The chase continues as the night wears on and tensions reach a peak.

Martina, Dawson, and Doughy eventually confront and defeat the killer. The killer is revealed as Hardy, Doughy's 'evil twin cousin,' and Hagitha accidentally shoots him. The trio breathes a sigh of relief as the danger appears to subside.

Outside Slab's house, Boner is found alive thanks to taking an entire bottle of Viagra, which keeps his blood pumping after his heart attack. A final call from the killer arrives, but Dawson hangs up and decides to follow the others to safety. The immediate danger subsides for now, but the threat lingers.

After the credits, a 'Where The Hell Are They Now?' tag reveals the fates of several characters and hints at a new killer reshaping the school’s future.