Marty Rantzen, also called himself "The Jester", is the main antagonist of the 1986 horror film, Slaughter High.
He was portrayed by the late Simon Scuddamore.
The day begins with a popular student, Carol Manning, jokingly asking Marty Rantzen, the school nerd, to have sex with her in the women's locker room. After he removes his clothes, Marty is surprisingly exposed to a group of students who tease him in several ways, including jabbing at his crotch with a javelin, giving him an electric shock and dunking his head into a toilet bowl. This prank ends when the students' coach comes in to find out what is happening.
The students are forced to perform a vigorous workout in the gymnasium. Still, two students give Marty a marijuana joint laced with poison, which he smokes in the science lab where he is working on a chemistry project. The joint makes him so sick, he runs to the men's room to vomit. While he is gone, Skip, one of the popular kids, rigs the experiment to explode in Marty's face.
Upon Marty's return, the set-up works, causing Marty to panic, and a great fire to erupt in the lab after he knocks over a Bunsen burner. In the struggle, Marty accidentally bumps into a shelf where a precariously placed jug of acid sits, causing the jug to fall and break, which splashes acid on Marty's face, leaving him horribly disfigured. The sound attracts the attention of the students, who stand by the door in shock.
Years later, those behind the prank are invited back to the school for a reunion. Upon arriving, they discover that the campus was shuttered years ago and the building is in disrepair, awaiting destructive demolition. They begin to think that one of the former students was behind the invitations, but everyone denies it.
They decide to break into the school to hang out and drink alcohol, and come across a room containing their old school lockers, which to their surprise are filled with their old belongings. They notice Marty's old locker, and the alumni begin questioning what happened to him after the prank-gone-awry. Skip tells them that Marty is doing fine and probably forgot all about what happened. He has supposedly been in a mental institution.
Soon thereafter, the friends begin to die in gruesome ways at the hands of a mysterious killer dressed like a jester. One's stomach explodes, one melts away in an acid bath, one is impaled on a javelin, one is chopped up by a riding lawn mower. They quickly come to believe it is Marty, deranged and bent on revenge. All of the former students wind up dead then come back as ghosts and the film closes with Marty apparently going insane. He wakes up in a mental hospital, restrained to a bed and wearing bandages on his face, and had in fact dreamed the events of the massacre.
The film ends with Marty strangling the nurse, jamming a syringe into the doctor's eye and peeling a chunk of skin from his own face.