Popcorn

Film student and aspiring screenwriter Maggie Butler (Jill Schoelen) has recurring dreams of a young girl named Sarah who is caught in a fire and being chased by a strange man who is trying to kill her. She records what she remembers on an audiotape and plans on making the story into a film. Maggie lives with her mother Suzanne (Dee Wallace Stone), who has been receiving demonic prank calls. On her way to class, Maggie shuns the advances of her boyfriend Mark (Derek Rydall), explaining that she can't be distracted from writing her script.

Maggie's classmate Toby D'Amato (Tom Villard) has an idea to put on an all-night horror movie marathon to raise funds for the university's film department. They set up shop in the defunct Dreamland theater, which is to be razed in three weeks. Professor Davis (Tony Roberts) is concerned about the time constraints, but Toby enlists the help of Dr. Mnesyne (Ray Walston), an owner of a film memorabilia shop, with deploying promotional gimmicks. There are three main films within a film: Mosquito is a 3D film, The Attack of the Amazing Electrified Man uses a "Shock-o-Scope" gimmick (electrical "buzzers" in seats), and The Stench uses Odorama.

As they go through Dr. Mnesyne's trunks of equipment, they find a short cult film called Possessor, which greatly resembles Maggie's dreams. Davis informs them Lanyard Gates, the film's director, killed his own family while shooting the final scene before setting the theater on fire, trapping the audience inside. Maggie soon becomes obsessed with Possessor and tries to figure out why she has been dreaming about it. When she asks her mother if she has heard of Gates or Possessor, Suzanne becomes uncomfortable; she urges Maggie to quit the festival and wants them to go away together. After Maggie goes to bed, Suzanne receives another prank call from someone she believes to be Gates. He tells her to meet him at Dreamland so they can talk and advises her to bring a gun.

On the night of the festival, Maggie is working the box office when Mark arrives with another girl, Joy (Karen Witter). Later, a man buys a ticket and calls Maggie "Sarah" before he walks away. Unable to find the man in the theater, Maggie goes to the projection booth to tell Toby that she thinks she saw Gates. Meanwhile, Mark has left his date to sneak up on Maggie and Davis prepares the giant mosquito model to fly across the theater that he operates with a remote control. Once the mosquito is released above the audience, a figure in the catwalks above Davis, using another remote control, uses the mosquito to stab Davis in the chest with the stinger. The scene cuts to a laboratory where a figure is seen making a mask of Davis's face.

As the second film starts, Bud (Malcolm Danare), who is wheelchair-bound, prepares the seat shockers from a control panel above the audience. Maggie listens to her audio recordings when the tape is cut off with a message from Gates. As she tries to exit the box office, she opens the door on Mark, knocking him down and unknowingly smashing the recorder in the process. Meanwhile, Maggie's classmate Tina finds Davis on the catwalk and goes up to meet him; it is revealed that they have been having an affair. She is unaware that the killer is posing as the professor, and is strangled with rope. Mark and Maggie find her shortly thereafter, but the killer manipulates her voice and body in the darkness to make it look like she is still alive.

The killer straps Bud into a makeshift electric chair that is set to go off when a series of lights comes on. As he is electrocuted, the theater loses power. Maggie finds her way to Bud, only to find him dead and Gates confronting her. As Maggie flees, she realizes that she is Sarah Gates, Lanyard is her father, and Suzanne is her aunt who saved her from being killed so long ago. She runs into Toby and tells him everything she remembers, believing that Gates has returned for her. She and Toby enter the basement and Toby falls, disappearing into the darkness. With only a flashlight, Maggie thinks she sees Davis and Tina, but runs into Gates. The power comes back on and Maggie finds herself in the killer's lair, strapped into the chair he uses to make facial masks of his victims.

The killer is revealed to be Toby, who was badly burned as a child after attending the showing of Possessor with his mother. Toby's mother was a member of Gates' film cult and was killed in the fire. Toby holds Maggie and Suzanne responsible for his loss, and plans to exact his revenge on them by re-enacting the final scene of Possessor onstage that evening, only with the ending that Gates had originally intended. He then wheels out Suzanne, whom he has cast full-body, pointing her gun.

Meanwhile, Cheryl and Joanie (Ivette Soler) tend to Mark's injuries as they are met with an upset Joy, who tells Mark she saw Maggie and Toby together and that they went back to Toby's place. Mark leaves to find them and Joanie realizes she is late for her Odorama cue and goes to join Leon (Elliott Hurst) to activate the odor pellets during the third film. Leon leaves to go to the bathroom and is met by a mirror image of himself at the next urinal. After urinating on him, the doppelganger attacks Leon and locks him in one of the stalls and drops some type of material into the toilet that creates a thick smoke and Leon passes out. Soon after, there is an explosion from the stall and Leon is killed. Toby returns to the booth dressed as Leon with the plan to stab Joanie from behind, but spares her when she mentions her unrequited love for Toby. Shocked by this, Toby gets upset and storms out to continue setting up for the final scene of Possessor.

Mark arrives at Toby's apartment to find that the landlord is evicting Toby. Toby's walls are plastered with articles concerning the incident, pictures of his facial reconstruction, and pictures of Maggie with scissors through her eyes. Realizing she is in real danger, Mark rushes back to the theater but the front doors are locked. He scales the building, climbs through a window on the balcony level and finds the final scene of Possessor playing on stage. Maggie has been drugged and placed in a metal dress so she has no mobility except for her head. She pleads to the audience to save her, but they believe this is all part of the show. Mark uses his belt on the mosquito track and zip-lines onto the stage, causing the secured mosquito to unlatch and swing out across the stage. The stinger stabs Toby in the chest, killing him. Mark releases Maggie and Suzanne as the crowd erupts in applause.