Corrine is the happily married mother of teenagers Christopher and Cathy, and five-year-old fraternal twins, Cory and Carrie. When her husband unexpectedly dies on his thirty-sixth birthday, Corrine is left penniless. With no place else to go, Corrine sells their belongings and returns to Foxworth Hall, the estate of her estranged elderly parents, Olivia and Malcolm Foxworth. Corrine explains that her parents disinherited her years ago, but she intends to win back her father’s love and become an heiress to his fortune. When the family arrives at the large, but decrepit mansion, Olivia Foxworth takes the four children to an upstairs room in a secluded portion of the house and locks them inside, instructing them not to yell, cry, or run. Although the room has windows, they are covered with bars, and very little sunlight gets in. When Olivia brings her grandchildren their first tray of food, she tells them, “Remember, God sees everything. God will see whatever evil you do behind my back and he will punish you for it.” She explains that their mother, Corrine, has come home after seventeen years to repent for her incestuous marriage to her uncle. However, Corrine’s father, Malcolm Foxworth, is dying, and Olivia does not intend to let him know that his grandchildren—“the devil’s spawn”— exist, in order to spare him the “final agony of shame.” In another part of the house, Olivia whips Corrine on the back seventeen times, one for each year of living in sin. When she takes Corrine to see the children, Olivia is offended by their glee at being reunited. When Cory bites her for hitting his twin Carrie, Olivia kicks and slaps him. She announces that she will provide them food and shelter, but no love or kindness, because she can feel only “disgust for what is not wholesome.” Olivia forces Corrine to show the children the bloody lashes on her back, to serve as a reminder that they must obey the rules. Christopher, who wants to be a doctor, tends to his mother’s wounds. Corrine confesses the years of happiness she shared with her husband were worth a hundred whippings, but she still intends to win back her father’s love. She asks the children to stay in the locked room until he dies. With Olivia’s permission, Corrine shows the children a secret passageway in the closet that leads to the attic, which they can make into a playroom. They clean out the dust and cobwebs, put up a rope swing, try on all the old clothes, and enjoy playing there. Finding leotards, Cathy starts practicing ballet. In the weeks that follow, Corrine rarely comes to see her children. Christopher worries that she is sick, or that Olivia has locked her in another room. Christopher and Cathy loosen a window bar and climb onto the roof, but when they shinny down a rope to the ground, guard dogs chase them back up. The next morning, Corrine visits her children, but chastises them for trying to run away. Her father’s doctors do not expect him to survive the month, so she asks them to hold on until the reading of the will. One night, as Cathy takes a bath, Christopher chats with her through the slightly ajar door. When their grandmother comes in, she is aghast at what she sees, but Christopher talks back to her. After Olivia leaves, Cathy worries that she will retaliate, but Christopher assures her that their mother will never let anything bad happen to them. Cathy is not so sure. The next day, Olivia cuts off Cathy’s shoulder-length blonde hair and refuses to feed the children for a week. As Cory gets weaker, Christopher takes the hinges off the door and explores the downstairs with Cathy. They are distressed to see the luxuriousness of their mother’s bedroom, and upset to find their grandfather is still alive. Cathy wants to take the twins and escape right away, believing their mother’s greed has changed her, but Christopher insists they wait for their grandfather to die. The next morning, Olivia resumes bringing them food, but laces the powdered sugar on the cookies with arsenic. When Corrine comes to see her children, she is excited because her father is throwing a party to reintroduce her to society, and rewriting his will to leave everything to her. Cathy complains about the living conditions in the “prison,” but Corrine calls the children “heartless” to think she does not love them. That night, the two teenagers slip downstairs and observe their mother having a wonderful time at the party. The next morning, as Cory becomes deathly sick, Olivia makes Corrine take him to the hospital, but Corrine returns to inform her children that Cory died of pneumonia. As the groundskeeper digs a grave for the boy, he also digs three others. A few days later, Carrie’s pet mouse dies after she feeds him part of a cookie, which alerts Christopher to the poison in the powdered sugar. Unbeknownst to them, it is Corrine who has been putting arsenic on the cookies. That night, when Christopher sneaks downstairs to look for money so they can escape, he discovers their grandfather has died and their mother is getting married to attorney Bart Winslow the next day. Finding a copy of his grandfather’s will, he reads that if it is proven, even after Malcolm Foxworth’s death, that Corrine had children from her first marriage, she will be disinherited. The children realize their mother never intended to let them leave the attic alive. The next morning, Olivia attacks her grandchildren with a meat cleaver, but they knock her unconscious and run downstairs. As the wedding begins in the parlor, Christopher, Cathy, and Carrie enter the room. As Corrine pretends not to know who they are, they accuse her of poisoning them and offer her a cookie. Cathy pushes her mother against the balcony, and when Corrine topples over the railing, her wedding veil gets caught in the trellis and strangles her. The three children leave Foxworth Hall. Although Carrie continues to be sickly, Christopher goes to medical school and Cathy becomes a dancer. They wonder about Grandmother Olivia, but never again have any contact with her.