Antoinette Cosway, a creole, or Caribbean person of European descent, recounts her memories of growing up at her family’s estate, Coulibri, in Jamaica in the 1830‘s. Her family, consisting of her mother, Annette, and her mentally disabled younger brother, Pierre, are destitute and isolated after her father’s death and the passage of the Emancipation Act of 1833, which freed Jamaica’s slaves. Annette becomes withdrawn and depressed, shunning Antoinette and talking to herself. Antoinette seeks refuge in the gardens and the company of her nurse Christophine, who is known for her practice of obeah, a voodoo-like folk magic. Antoinette has a short-lived friendship with a little black girl, Tia, until the two fall out over a bet while they’re swimming, and Tia runs away with Antoinette’s money and clothes. After seeing Antoinette in Tia’s dirty dress, Annette resolves to lift the family out of poverty. She soon marries Mr. Mason, a wealthy Englishman. Mr. Mason has Coulibri completely renovated. The show of ostentatious wealth causes resentment in the neighboring village of poor ex-slaves. Annette and Aunt Cora, fearing retribution, urge Mr. Mason to move the family out of harm’s way, but he ignores them. One night, a mob sets fire to the house at Coulibri. The family narrowly escapes, but Pierre is badly injured. Antoinette descends into a fever for six weeks. When she finally awakes, she learns that Pierre has died, and that her mother Annette is being kept at a convalescent house in the country. Antoinette goes to visit her, but finds her mother unrecognizable, mad with grief.
Antoinette begins to attend an all-girl’s convent school. The nuns there instill the values of chastity and good behavior in their students, and place a high premium on appearance. Antoinette is comforted by the routines of the convent, but fails to find faith or solace in prayer. After eighteen months, during which time Annette has died, Mr. Mason comes to visit her and informs her that he is taking her out of the convent school, implying that there is a suitor waiting for her. Antoinette has a recurring nightmare about a stranger leading her through the woods and up a flight of stairs.
Part Two of the novel begins during Antoinette and her new husband’s honeymoon, on the island of Granbois, near Jamaica. This section is narrated from the point of view of the husband, an unnamed Englishman who feels menaced by the strange landscape, language, and customs of the Caribbean. He distrusts the servants, particularly Christophine and the young and defiant Amelie. He has married Antoinette for her money, and sees her as a beautiful but unsettling stranger. The two spend afternoons swimming and nights making passionate love, until one day the husband receives a letter from Daniel Cosway, who claims to be Antoinette’s half-brother, the product of an illicit relationship between her deceased father, Old Cosway, and one of his slaves. The letter warns the husband that madness runs in the Antoinette’s family on both sides, relating rumors that both Antoinette’s mother and father died “raving.” Daniel Cosway insists that Antoinette’s family, especially Richard Mason, deceived the husband when making the marriage arrangements. The husband does not mention this letter to Antoinette, but becomes distant and cold. Christophine leaves Granbois because of her dislike of the husband, which devastates Antoinette. Shortly after Christophine’s departure, the husband gets lost in the woods and is sure he sees a ‘zombi,’ or the walking dead, near an abandoned house. He is finally found by Baptiste, the butler, who refuses to answer his questions about the house.
The narration switches to Antoinette’s point of view. She goes to Christophine’s house to beg her to use obeah to make the husband love her again. Christophine refuses at first, advising Antoinette to act for herself. Antoinette eventually wears her down, though, and Christophine supplies her with a bottled liquid.
The narration shifts back to the husband’s point of view. He goes to see Daniel Cosway, who attempts to blackmail the husband into giving him 500 pounds. That night, the husband and Antoinette argue, and he demands to know the truth about her past. She tells him of Coulibri burning, Pierre’s death, and her mother’s descent into madness. It is revealed that her mother was sexually abused at her convalescent home. The husband begins to call her Bertha, which disturbs her. The two go to bed, and Antoinette hands him a glass of wine, after which point the husband loses all memory of the rest of the night. The next morning, he realizes that Antoinette has drugged him, and runs into the woods. When he returns, Amelie tends to him, and they sleep together. When he emerges from his room, Antoinette, who listened to their tryst from the next room, has fled the house. She returns with Christophine several days later. As a distraught Antoinette barricades herself in her room and drinks to excess, Christophine and the husband argue. When the husband threatens to go to the police and report her practice of obeah, Christophine, though outraged, has no choice but to relent. She leaves without saying goodbye to Antoinette. The husband decides that they must leave Jamaica. Antoinette is numb and silent on the day of their departure. The husband is overtaken with remorse, but the hatred between himself and Antoinette soon outweighs it.
Part Three opens in the point of view of Grace Poole, Antoinette’s caretaker in England. It is revealed that Antoinette is being kept against her will in the attic of the husband’s house, in conditions that make Grace Poole uncomfortable, but she is paid twice what the other servants are for her silence.
The narration switches to Antoinette’s consciousness. She is unsure of where she is or how much time has passed. She often steals Grace Poole’s keys and explores the rest of the house at night. One day, Grace Poole tells her that the night before she, Antoinette, was visited by Richard Mason and attacked him with a knife. Antoinette does not remember this. That night, she has her recurring nightmare for the last time. It is clear that the stairs she has dreamt of her whole life have led here. In this version of the dream, she takes a candle and sets fire to the house, sits out on the roof watching it burn while recalling the fire at Coulibri. In the dream, she hears the husband calling to her and jumps to her death. When she wakes, she is filled with a sense of purpose, lights a candle and descends into the house to act out her dream.