A large group of college students are at a bonfire for the New Year's Eve celebration. All of the pledges are wearing beanies, and one socially awkward taciturn pledge named Kenny (Derek McKinnon) is sent by the fraternity president Doc (Hart Bochner) and his friends up to a room in the frat house where a sorority sister named Alana (Jamie Lee Curtis) is waiting in the doorway. Alana walks inside the bedroom and stands behind the canopy in the dark room. Kenny undresses to his underwear, sits in bed, and realizes that he is sitting beside a bloated and rotting corpse. Kenny screams in terror and he stands up on the bed and is caught up in the canopy. Alana seems repulsed as Doc and a group of other students rush in and laugh at Kenny.Three years later.A large group of college kids are exiting a bus at a train station. They have a toast celebrating four great years at college as they prepare to board a charted old train for a New Year's Eve costume party. Carne (Ben Johnson), the lead conductor, has the students board the train while he organizes the route with the dispatcher. Carne helps a magician (David Copperfield) and his assistant carry their luggage on board, as a three-person band board the train for the excursion.Nearby, Ed (Howard Busgang) a prankster student and one of the ones involved in the prank against Kenny, walks around with a sword through his stomach. The other students laugh and think its another one of his practical jokes, but he falls down after the people walk away and board the train. An unseen person takes Ed's Groucho Marx costume and rolls his dead body under the train tracks. The train leaves and the lights at the deserted station are turned off. The killer is wearing Ed's costume as he moves around the train.Meanwhile, Mitchy (Sandee Currie) another one of the students involved in the prank against Kenny, is talking to Alana who is graduating early and hopes they will keep in touch.In the back of the train, the magician is talking to his blond assistant about the rowdy college kids and complaining about having to perform his illusions in front of them.In the lounge car, Doc is celebrating with his fellow frat brothers when one of them asks about the now abolished "hog night" and he mentions that something bad happened. Alana enters and tells them that they "put a kid in the hospital" who had a nervous breakdown due to Doc's prank three years ago. Alana then goes to her boyfriend Mo, also involved in the prank against Kenny, where they retire for some alone time.A little later, Mitchy sees 'Ed' and he follows her towards the sleeping berths. He nearly grabs her when Jackson, another of the students involved in the prank against Kenny, appears. Jackson is very inebriated and he offers 'Ed' a drink. In the nearby lavatory, the killer grabs Jackson, lifts up his mask for a second to let him see his face, and slams Jackson's head into the mirror. The killer then changes out of his Groucho Marx costume and leaves the lavatory.Meanwhile, Alana becomes angry when learning that the train party was Doc's idea after Mo told her that it was his. Two of the sorority sisters, Pet and Merry, show up where Pet thinks that her boyfriend, Ed, missed the train, and Alana argues with Mo about learning that Doc had set him up again. Carne, the conductor, shows Doc and Mitchy a car trick he learned form the magician (it is only a gag), and the couple waits for the occupied bathroom. After a few minutes, they leave to find another one.Later, the magician performs his show before the students and afterwards, the rock band appears to play. Alana talks with the geek class president (who was a pledge in the opening scene). Meanwhile, Doc asks Mo where Jackson and Ed are. Mo does not know and when he asks where did he find the magician, Doc says that he did not hire a magician for the party and wonders who did.Alana tells Carne that someone may have been left behind, but Carne tells her that the train platform was empty when he viewed it prior to the train leaving. Mitchy hears this and tells them that she saw Ed earlier on the train. Frustrated at being unable to find their boyfriends Jackson and Ed, Merry and Pet approach Doc and Mo who offer to take them to "consulting rooms" as they are both med students.Carne goes off to have a talk with Walter, the engineer of the train, and the stoker, nicknamed Shovels, to ask for the time to reach their destination. Carne then tries his card gag on Charlie, the brake master, who does not understand the joke.Afterwards, Carne then goes to the locked door of the lavatory and knocks on it, asking if there is anyone inside for it has been locked for some time. He unlocks it with his master key and finds a dead Jackson lying on the floor, with blood everywhere. Carne checks and sees that his neck must have been slashed and he quietly locks it again. Carne then tells Walter and Charlie what he found saying "there's a boy dead back there". After looking at a map of the area, they agree that the closest way out is straight ahead as the train is moving though rural and unpopulated wooded areas.Back in the showroom car, Mitchy mentions to Alana on the dance floor that she is leaving to be with Doc, and the magician, after looking at Alana, leaves in the same direction at Mitchy.Charlie arrives at the locked door to the lavatory and tells some girls passing by that it is out of order. Carne opens the door for him and the blood is gone and 'Jackson', wearing his alligator costume, is down on the floor moving. Carne thinks it was a practical joke and Mitchy walks by and leads 'Jackson' away.In Doc and Mo's room, Merry points out Kenny's photo in a yearbook. When Mo mentions about Kenny having a nervous breakdown, Doc yells at Mo not to talk about it, and Pet motions for Doc to keep quiet. Doc and Merry leave Mo alone with Pet.At the same time, Mitchy is with the killer still wearing Jackson's alligator costume, unaware of who it really is. Mitchy beckons him to join her in a berth bed as Merry and Doc walk by. Mitchy leans down and asks 'Jackson' to have her way with her. The killer takes off a glove and lays a hand on Mitchy's chest. She looks down and sees that it is Jackson's severed hand. She tries to scream, but the killer puts his real hand over her mouth.A little later, the magician approaches Alana and asks if she enjoyed his show, and he tries to woo her with more illusions such as the cigarette-through-a-quarter trick, and a levitating rose. Doc sees this and interrupts the conversation to tell Alana that Mo is waiting for her. Doc, for some reason, is not friendly towards the magician.Meanwhile, Carne finds one of Mitchy's shoes on the floor in the sleeping quarters and then finds Mitchy dead with her throat slit in one of the beds. He runs into Alana and asks her whose shoe he has. She goes to get Mo, but he ignores the knocking at his door for a rambunctious Pet is there with him. Carne gets Alana alone in the conductor car and tells her that Mitchy is dead and he shows her the body.The magician puts on a second show where he asks Merry to volunteer for some of his illusions. Doc continues acting in a rude tone around the magician and outright expresses skepticism to the show. After a few minutes, Doc sees Mo hanging his head out of apparent boredom and follows suit. When the magic show ends, Mo does not move or talk, and when Doc hits him, he falls over. Doc takes a closer look at Mo and sees that he is not breathing. Doc's screams for help are ignored by the crowd as they cheer for the magician and his assistant. Doc carries Mo through the train to Carne and Alana and they discover a large stab wound on his chest. Mo is dead.Finally aware that there may be a maniac killer on board the train, Carne checks the lavatory and discovers a bloodied rag that the killer used to clean up the mess after killing Jackson. Carne runs up to the engine room only to find Walter and Shovels both gone (only finding a bloody engineer's cap). Carne and Charlie pull the emergency breaks and, after a tense minute, stops the train. Carne leads the students off the train as he has the chief porter and several of his men look around the train for the killer. Outside, Carne has everyone take off their masks to get a look at all of them as the class president takes a roll call to see who is present.Alana suggests to Doc that the killer might be Kenny wanting to get back at all those involved in the prank against him three years earlier. She tells Doc that after the practical joke with the corpse, Kenny was taken away and when she went to the hospital psych ward later that night to visit him to apologize for the prank, the hospital staff would not let her see Kenny for he was being kept in isolation because they told her that Kenny had accidentally killed someone before when he was younger (either his mother or a female relative in a car accident). Apparently the site of the rotting female dead body triggered a total relapse of Kenny's mental breakdown and he is now getting revenge against all of those involved in the prank against him. Doc thinks that with Ed, Jackson, Mo, and Mitchy dead, they are the only two ones left involved in the prank and they might be next.Doc takes Alana to a room on the train and locks the doors. He shows her a yearbook and she sees that Kenny used to be a magician in high school. Alana wants to tell Carne about Kenny, but Doc refuses to let her leave. She gets out of the room and runs when a figure wielding an ax approaches her. But it is only Charlie the break master who tells her to go back outside with the others.Alone in the room, Doc checks every inch of the room from the lockers to the above berths. He sits down and then realizes that he forgot to check under the seats. He stands up and is grabbed by someone under his seat. He tries to escape, but a hand grabs his shoulder. He looks at the hand which has painted black fingernails and Mitchy's class ring. He settles down believing that Mitchy is joking with him. But the killer pulls out a knife and puts it to his neck and slashes his throat.Carne takes the students back onto the train and has them all packed into the dining room car to sort out who the killer is. With no phone or radio and no roads around, they will have to travel to their destination to find help. Meanwhile, the magician's assistant arrives back in the showroom car and tells him about a killer lurking among them, and he scolds her for wondering around and going outside.As Carne has Charlie restart the train and as it gets underway again, Alana runs up to him and tells him that she thinks the killer is the magician. They go to get Doc, and Carne enters the dark cabin room to find it splattered with blood and he finds Doc with his head cut off in one of the berths.Carne assembles a small group of train porters who arm themselves with fire axes and crowbars. They quietly enter the magician's showroom car where they herd his assistant and all of the students out, and lock the door. The chief porter takes Alana to a compartment and offers to look after her while she rests. Having assembled all of the students into the tightly packed dining room car, Carne and his men enter the showroom car, but the magician is nowhere to be found.In the rooms compartment, the chief porter is sitting dead in a chair... having been stabbed with one of the magician's swords. The killer is now wearing Mitchy's black robe and old man's mask costume and, taking the ax off the dead porter, quietly enters Alana's room and swings the ax at the covers, but it is only an inflatable doll. Alana, anticipating the killer would do just that, jumps out of a closet and stabs the killer in the shoulder with a sword. But the killer gets back up and chases her to the conductors car, but loses his ax when he swings and misses Alana and it flies out a window. Deprived of his weapon, the killer and Alana struggle with him trying to choke Alana. Alana sprays the killer with a fire extinguisher and takes refuge in a caged area with a desk. She locks herself in, and the killer arms himself with a crowbar and knocks out all the lights in the compartment and attempts to pry the lock. But Alana stabs him in the face with a letter opener, kicks the door open and runs out. The killer chases Alana and, during another struggle, falls between the train cars. Carne and his men arrive and leads the wounded and shaken Alana away, unaware that the killer is holding onto the side of the train car.Later, as dawn begins to break, Alana sits alone in the back of the train in the show room and upon looking at the magician's folder and paperwork, finds the magician dead in a box, impaled with his swords. Alana screams, and runs out past the students and goes forward to the conductors compartment at the front of the train to find Carne and sees Charlie sitting at his desk. She tells him that the magician is dead and doesn't know who the killer is anymore. But the figure grabs her hands and she looks up and sees a masked person wearing Charlie's uniform. The killer had obviously killed Charlie, removed his uniform, and threw his body off the train for the side car door is slightly open. Alana asks the killer who he is, and he removes his mask, revealing a pasty white-faced Kenny (complete with a wound to his left cheek where she stabbed him earlier). Kenny then takes off his cap, revealing.... flowing blond hair (a short subliminal montage reveals that Kenny was half the time in disguise as the magician's female assistant). Kenny takes off the blond wig, removes his false teeth and wipes off his lipstick and white powder makeup. Alana tries to apologize to Kenny for her involvement in the prank, but he tells her that he always had a crush on her. He tells her to kiss him for he feels that Alana owes him just that for the past three years, and she reluctantly obeys. Suddenly, Kenny has a similar eerie reaction as the memory of the practical joke with the corpse comes right back to him. Alana backs away and Carne enters from the engine room with a shovel and sees Kenny reacting to his encounter with Alana. Carne hits Kenny with the shovel, and he falls out of the moving train though the open side door while it is passing a bridge. Kenny falls hundreds of feet and lands (presumably dead) in an icy river far below as the train continues moving on.