In 1967 New England, aimless 18-year-old Susanna Kaysen has a nervous breakdown and overdoses on aspirin, after which she is checked into Claymoore, a local psychiatric hospital. Previously, she had an affair with Professor Gilcrest, an English instructor, as well as a casual relationship with a boy, Toby. In the ward, she befriends Polly Clark, a childlike schizophrenic; Georgina Tuskin, a pathological liar and Susanna's roommate; Daisy Randone, who self-harms and has obsessive–compulsive disorder; and Janet, a sardonic woman with anorexia. Susanna is particularly drawn to sociopath Lisa Rowe, who is rebellious but charismatic and encourages Susanna to stop taking her medication and resist therapy. Lisa has been at Claymoore for eight years and knows how to manipulate the system.
Lisa helps the girls sneak around at night in the hospital's underground tunnels and constantly provokes them and the staff, including the stern head nurse, Valerie. Through regular therapy sessions with Dr. Melvin Potts, Susanna comes to learn she has borderline personality disorder, a fact Dr. Potts initially keeps concealed from her. On a rare supervised group outing celebrating Daisy's impending release, the women visit an ice cream parlor in town. There, Susanna is confronted by Barbara Gilcrest, wife of Professor Gilcrest, and their daughter, Bonnie. Barbara publicly chastises Susanna for sleeping with her husband; coming to Susanna's defense, Lisa insultingly berates Barbara and the other girls mock her and Bonnie before they both leave, humiliated. This endears Susanna to Lisa even more, though Valerie reprimands Lisa.
One day, Toby, who has been drafted to serve in the Vietnam War, visits Susanna, begging her to run away with him. She tells him she has become friends with the other girls and would like to leave someday but not with him. That night, Polly has a breakdown and is placed in isolation. Susanna and Lisa drug the night watch nurse with a sedative and attempt to comfort Polly by singing to her. Susanna makes out with John, one of the hospital orderlies who has a crush on her. When Valerie finds the group sleeping in the hallway in the morning, she punishes the two women, particularly Lisa, who is forced to endure electroshock therapy followed by solitary confinement.
Later that night, Lisa manages to break out of confinement and convinces Susanna to escape with her. The women hitchhike to Daisy's newly rented apartment, supplied by her doting father, and bribe her with valium to spend the night. Daisy, insistent she has been cured of her illness, is confronted by Lisa when Lisa discovers Daisy has been cutting herself. Lisa taunts Daisy, accusing her of enjoying the incestuous sexual abuse she has long suffered from her father. The next morning, Susanna finds Daisy dead in her bathroom, having slashed her wrists and hanged herself. Susanna is appalled when Lisa searches Daisy's room and body for cash. Realizing she does not want to become like Lisa, she phones for an ambulance and returns to Claymoore, while Lisa flees to Florida.
Back at the hospital, Susanna occupies herself with painting and writing, and cooperates with her therapy, including regular sessions with the hospital's head psychologist, Dr. Sonia Wick. Before Susanna is released, Lisa is apprehended and returned to Claymoore. She steals Susanna's diary one night and reads it for the amusement of the patients in the tunnels, turning them against Susanna. After reading an entry in which Susanna feels sympathy for Lisa being a cold, dark person, Lisa attacks Susanna and chases her through the tunnels. Cornered, Susanna confronts Lisa, accusing her of being dead inside, emotionally dependent on Claymoore, and afraid of the world; this profoundly affects Lisa, who breaks down and attempts to commit suicide, but the others dissuade her from doing so. Before Susanna is released the next day, she goes to visit Lisa, who is restrained to a bed. The two reconcile, and Lisa insists she is not actually heartless.
Winona Ryder as Susanna Kaysen,
Angelina Jolie as Lisa Rowe,
Clea DuVall as Georgina Tuskin,
Brittany Murphy as Daisy Randone,
Elisabeth Moss as Polly "Torch" Clark,
Angela Bettis as Janet Webber,
Jillian Armenante as Cynthia Crowley.
Travis Fine as John,
Kurtwood Smith as Dr. Crumble,
Jeffrey Tambor as Dr. Melvin Potts
Joanna Kerns as Annette Kaysen,
Ray Baker as Carl Kaysen,
Jared Leto as Tobias "Toby" Jacobs,
Vanessa Redgrave as Dr. Sonia Wick,
Whoopi Goldberg as Valerie Owens, R.N.
Bruce Altman as Professor Gilcrest
Mary Kay Place as Barbara Gilcrest,
KaDee Strickland as Bonnie Gilcrest,
Robin Reck as Theresa McCullian.
Misha Collins as Tony
Based on Susanna Kaysen's memoir of the same name