Susanna Kaysen is a young woman of eighteen, and her life isn't exactly what a normal eighteen-year-old's life is suppose to be like. To her, any kind of sex is casual, and it doesn't matter who she does it with or when, as long as she gets it. At graduation, she falls asleep, proving she has little interest for the norms of prize-givings or anything to do with what's accepted by society. At her father's birthday party, she is under dressed and is of course moaned at by her hypocritical mother. Here we learn that her parent's friends are just as false as what is accepted by everyone. And then it becomes clear that Susanna has been sleeping with her mother's friend's husband.This drives her to try to commit suicide with aspirin and a bottle of vodka to get it all down. At the ER, she claims that she doesn't have bones in her wrists anymore, and tells the psychiatrist at home that the bones grew back by the time she got to the hospital. So she is shipped off to Claymoore, a local mental institution and put in the ward for women only. Here she meets a multitude of people who really do have problems: a sardonic anorexic, a girl who burned herself as a child, a lesbian (at the time was thought of as a mental disorder), a bulimic, and her roommate, a compulsive liar.The ward is managed by Nurse Valerie Owens, who is very clever, but is unable to become a doctor due to her race. All the nursing staff and the patients are kept marginally sane by Valerie, and she and Susanna have a complex relationship. Susanna is questionably diagnosed with having borderline personality disorder. Things really get started when the sociopath runaway patient, Lisa Rowe, returns to the ward and turns Susanna's world upside down and inside out. She is a force to be reckoned with - she is magnetic, rebellious, doesn't take her meds and is unhealthy for the other patients as she breaks down their self-esteem regularly. Due to the fact that her last best friend, Jamie, couldn't hack this when she ran away, Lisa befriends Susanna and together they start a world of trouble.Susanna keeps a diary of all her thoughts and feelings, also illustrating in it, and telling the tale of her stay through her daily entries. Her ex-boyfriend, Tobias Jacobs, comes to visit her and she very nearly tries to have sex with him in her room. He tells her he wants them to run away to Canada together so that he doesn't have to go to Vietnam. He tells her she isn't crazy and that the girls in the institution aren't really her friends. But she refuses to go with him, subconsciously beginning to rely on Lisa.Then she meets the head psychiatrist, Dr. Sonia Wick, and claims she is ambivalent, saying it means she doesn't care. But Dr. Wick sees through this mask and decides to have Susanna see her from now on. Afterwards, Lisa is taken into see the doctor, but doesn't return and Susanna falls into a depression. Nurse Valerie has had enough and throws her into an ice cold bath to wake her. She tells Susanna, after Susanna attacks her verbally and says that she doesn't know what she is doing, that she is a spoiled, lazy little girl who is driving herself crazy! And that if Susanna isn't careful, she will throw her life away on some stupid rebellion.That night, Lisa breaks into the ward, wild-eyed and crazy, and Susanna runs away with her so they can get to Disneyland. There they hook up with hippies and eventually crash at the bulimic Daisy's house after bribing her with promises of meds. But all turns bad when Lisa tells Daisy that she is a freak herself and that this apartment is all a mask to hide what's really happening. She breaks Daisy down, finally saying that Daisy probably likes her father molesting her and that it's probably all she has ever known. The next morning, Susanna wakes up and goes for a walk, to escape the sound of Lisa's voice and returns to find Daisy playing a record over and over again and Lisa in the kitchen. She goes up the stairs and finds Daisy's wrists slit and she hangs herself in the bathroom. Susanna goes back to the institution without Lisa, (who runs away again) and begins anew with Dr. Wick and her diary.When Susanna is ready to leave, Lisa breaks out of her padded cell and steals Susanna's diary. Beneath the ward in the maze of corridors, Lisa reads the diary aloud and tells the other girls what Susanna thinks of them. Susanna runs away from Lisa when she begins to chase her with a needle filled with a toxic-looking chemical. Susanna breaks her hand while trying to close a sliding metal door on Lisa and then they finally confront each other. Susanna finally tells Lisa that no one cares if she dies because she is already dead and her heart is cold. She also tells Lisa that she will begin her life again out of this hospital without Lisa and the others. Lisa has a mental breakdown and attempts to commit suicide but the other girls dissuade her from doing so.In the morning, Susanna is about to leave, but first she goes to visit Lisa and talks to her again. Now restrained to a bed, Lisa says that she isn't really cold and that she didn't mean to hurt Susanna. When she leaves, she says goodbye to all her friends, and gets into the taxicab saying that being crazy isn't about keeping a secret, it's just about everyone being personified. And by the seventies, most of her friends were out of the institution and leading lives. The girl who was just interrupted by herself and everyone else, is finally recovered from being a supposed borderline.