As a child, Jeannette Walls lives a nomadic life with her painter mother Rose, her intelligent but irresponsible father Rex, older sister Lori, and younger brother Brian. While cooking unsupervised, Jeannette is severely burned. At the hospital, a doctor and social worker question her home life, but Rex distracts the staff and escapes with Jeannette. The family leaves town, and Jeannette is enchanted by Rex’s plans for the family’s dream house, a glass castle.
The family soon includes Jeannette’s infant sister Maureen, and remains on the move for years, eventually relocating to a dilapidated house in Utah. Jeannette nearly drowns when a drunk Rex aggressively teaches her to swim. He assaults the lifeguard, forcing the family – now pursued by the law and with no money – to go to Welch, West Virginia, where the children meet their grandparents and uncle Stanley. Rex moves his family into a ramshackle house in the wilderness, living without running water, gas, or electricity. When the family has not eaten in days, Rex takes their remaining money to buy food, but returns home drunk after a fight. Sewing up his wound, Jeannette asks him to stop drinking, and Rex ties himself to his bed, successfully enduring withdrawal. He lands a job as a construction worker and the family enjoys a comfortable Christmas.
The parents attend the funeral of Rose’s mother in Texas, leaving the children with their grandparents in Welch. The sisters discover Irma sexually assaulting Brian and attack her, but are pulled away by Stanley. When their parents return, Rex refuses to listen to his children about the incident. The family returns home and he resumes drinking, leading to a violent altercation with Rose. Jeannette is unable to convince her mother to leave Rex, and the siblings promise to care for each other and escape their poverty.
As a teenager, Jeannette is drawn to journalism. The siblings save enough money for Lori to leave for New York City, infuriating Rex; Jeannette prepares to do the same. Irma dies, and after the funeral, Jeannette is pulled into her father’s scheme to hustle his acquaintance Robbie at pool. He loses to Rex and reveals Jeannette’s plan to move to New York City. She accompanies Robbie upstairs and he attempts to rape her, but she shows her scars from her childhood burns and leaves. At home, she discovers her father has stolen her savings, but escapes home anyway. Attending college in New York City, Jeannette faces financial difficulties and prepares to drop out, but Rex arrives with a pile of gambling winnings, telling her to follow her dreams.
By 1989, Jeannette is a gossip columnist for New York magazine and engaged to marry David, a financial analyst. At dinner with a client of David’s, Jeannette lies about her parents. On the way home, she sees her now homeless parents dumpster diving. She later meets with her mother, who is dismissive of her engagement. Jeannette and David visit her family at the abandoned building where her parents are squatting. Brian, now a police officer, and Lori live comfortably, but Maureen has moved in with their parents. Rex and David drunkenly arm wrestle and David wins, but Rex punches him in the nose. Returning home, David tells Jeannette that he wants nothing more to do with her parents.
Maureen calls Jeannette to explain that she is moving to California. At her engagement party, Jeannette discovers that her parents have owned valuable land – now worth almost $1 million – since she was a child, but chose never to sell. Furious at Rex’s refusal to admit to the pain he caused his family, Jeannette bans him from her life. Some time later, Jeannette is unhappily married to David. Rose reaches out to tell her Rex is dying, but Jeannette refuses to see him. At dinner with another of David’s clients, Jeannette finds the courage to reveal the truth about her parents. She races to her father, and they reconcile before he dies. The following Thanksgiving, Jeannette – now a freelance writer living alone – celebrates with her family, reminiscing about Rex’s unconventional life.