Dancer Kelly McIntyre arrives late to her job at Demons discotheque due to a fight with her boyfriend, Ronnie Denton. Before starting her shift, Kelly grabs a drink from the bar. Later, as she dances, she has a seizure and is taken to a nearby hospital. There, doctors diagnose her with strychnine poisoning, the sign of a suicide attempt. After four days in intensive care, Kelly awaits discharge, but Ronnie informs her doctor that she attempted suicide as a teenager. Kelly insists that she was poisoned, but then experiences a hallucination, and the doctor decides to hold her for further observation. Kelly is admitted to the fifth floor psychiatric ward, where a medical technician named Carl escorts her to see a psychiatrist, Dr. Sidney Coleman. When Kelly explains to Dr. Coleman that she had no intention of killing herself, the doctor reports that no trace of strychnine was found in her drink. Kelly argues that the person who put the poison there removed the evidence. After further conversation, Dr. Coleman discovers that Kelly had a fight on the night of the incident, and the police report makes mention of a coworker, who claims that Kelly voiced a desire to end her life. Kelly responds that she made the remark in frustration but had no intention of committing suicide. However, the doctor explains that the law requires him to determine that she is not a danger before she is discharged. If she refuses to cooperate, she will be held against her will for seventy-two hours so that a diagnosis can be made. Later, Kelly attends a group therapy session where a pregnant patient, Cathy, describes how she killed her boyfriend, Terry, in a car accident while driving under the influence of drugs. The next day, Kelly learns that the court will take custody away from Cathy when she has her baby, so Kelly promises to find Cathy a good lawyer upon leaving the hospital. When nurse Jackie Hanneford overhears the conversation, she warns Kelly not to interfere with the court’s orders. Soon, Carl escorts Kelly to the shower because an attendant has to be present in case she has a seizure. When Kelly drops the soap, Carl grabs it, soaps her back, and she narrowly avoids being raped by running to the patients’ lounge. There, she explains to the nurses how Carl tried to harm her, but Carl chalks it up to a “paranoid episode.” As Kelly is restrained and tranquilized, she cries that Carl is lying. When staff members review Kelly’s outburst at their meeting, Carl suggests Kelly fantasized that he fondled her and says that he did not request help from a female nurse because he was afraid Kelly would go into convulsions. When nurse Hanneford tells Dr. Coleman that Kelly is sticking to her story, he decides to keep her under observation for another two weeks. Dr. Coleman warns Carl that if he is found abusing patients, he will be fired and charged with a felony. At night, Carl visits Kelly and apologizes for his behavior. After he leaves, her roommate, Melanie, confesses that she too rejected Carl when she was first admitted, but he later raped her and warns Kelly to do everything in her power to escape the institution. Ronnie visits Kelly, feeling guilty that their fight might have provoked her “attempted suicide.” When Kelly reveals she was almost raped in the shower, she pleads with Ronnie to help speed up her discharge, but nurse Hanneford interrupts, asking Ronnie to leave. Meanwhile, Melanie has a fight with visitors and Kelly prevents her from swallowing pills, only to have Carl take Melanie for additional therapy. Afterward, Carl tucks comatose Melanie to bed and offers Kelly a chocolate bar, which she refuses. In the lounge, Kelly teaches the other patients disco dancing until Carl orders them back to their rooms. Kelly, in turn, asks Carl to meet her in secret at night. She lures him into a dark room, where he drops his pants anticipating sexual favors, but instead, the light is switched on. Carl is surrounded by laughing mental patients, so he runs out of the room. On an outing to the zoo, Carl tells Kelly her joke was funny, but he might have a funny one for her. She runs away from hospital chaperones, hitching a ride before Carl can catch her. She takes refuge in Ronnie’s apartment while he is out, and packs her clothes in a suitcase. Ronnie is surprised to see her when he comes home, but the more Kelly tries to convince him of her sanity, the less compassionate Ronnie appears. Kelly ends up back in the psychiatric ward, restrained by a straight jacket. In addition, she receives a condescending lecture from Dr. Coleman about being her own worst enemy as he informs her that she will stay in the psychiatric ward for ninety days. Soon, Kelly has another setback when her troubled roommate, Melanie, hangs herself. The doctor prescribes hydrotherapy for her rattled nerves and Carl comes to chat while Kelly is soaking in the tub. He force feeds her drugs, submerges her head under water repeatedly, then rapes her. In the morning, she convinces a patient named Benny to escape with her. The other patients create a diversion so that Benny, Kelly and Cathy Burke can steal an ambulance that Kelly drives to the discotheque. There her friend, Jinny, explains that Hal, the owner, was arrested for the strychnine poisoning after it was discovered that he was trying to get rid of a worker who blackmailed him. Kelly leaves with some money, and gives Benny and Cathy a different car in which to escape. However, police and Carl surround Kelly, and she is sent back to the psychiatric hospital, where she is subjected to electroshock treatment by Carl. A patient stabs Carl in the stomach after seeing how he mistreats Kelly. Later, Kelly is released after spending ninety days on the fifth floor through a court order submitted by Ronnie.