The year is 1859, and Grace Marks has served many years of a life sentence, which she earned for her involvement in the murders of a wealthy gentleman named Thomas Kinnear and his housekeeper, Nancy Montgomery. Grace has proven herself a model prisoner, and, as a result of her good behavior, the Governor who runs the penitentiary has granted Grace permission to spend her days working as a housekeeper in his own home under the supervision of his wife. The Governor’s wife belongs to a group that advocates for social reform. This group, which includes Reverend Verringer, believes in Grace’s innocence and has made numerous failed attempts to win her a pardon. However, interest in Grace’s case is revived when a doctor named Simon Jordan comes to Kingston to work with her.

Dr. Jordan trained as a medical doctor, but his interest has since shifted to psychology. Grace claims to have forgotten the events surrounding the Kinnear–Montgomery murders, and Dr. Jordan hopes to use newly developed techniques to help restore her memory. If he achieves his goal, not only will he confirm Grace’s guilt or innocence, but he will also have evidence on which to build a theory about the mysterious workings of the human mind.

Dr. Jordan meets with Grace in the afternoons in the sewing room at the Governor’s house. Grace initially finds it difficult to trust Dr. Jordan, partly due to a general wariness about doctors and partly due to skepticism about his intentions. He also exhibits what Grace considers odd behaviors. For instance, he presents Grace with seemingly random objects, and he asks what associations these objects bring up for her. Dr. Jordan hopes that his associational technique will allow subconscious memories to rise to the surface. Grace slowly warms up to Dr. Jordan, and she agrees to recount her life story leading up to and including the murders.

The rest of the novel moves back and forth between present events and Grace’s account of the past. The narrative also shifts between a first-person account from Grace’s point of view and a third-person account from Dr. Jordan’s point of view, allowing the reader to see the unfolding events from multiple perspectives. Grace recounts the story of her life in great detail, starting with her childhood in Ireland and the story of her mother’s marriage to an irresponsible alcoholic. Unable to support their quickly growing family, Grace’s parents moved their family to Canada, which promised ample opportunities for land and work. However, Grace’s mother died on the journey across the Atlantic, and Grace’s father quickly resorted to his old ways after arriving in Toronto and forced Grace to find work.

Grace became a live-in servant in the home of a wealthy Toronto family, where she befriended a maid named Mary Whitney. Outspoken in her critiques of the upper classes and particularly of gentlemen, Mary amused and shocked Grace. But Mary also showed Grace kindness and support, teaching her what she needed to know and acting like a surrogate mother. Tragedy struck when Mary became pregnant by one of her employer’s sons, who refused to marry her. She got an abortion, but the operation killed her.

In her grief, Grace sought work elsewhere. She soon moved out to the rural village of Richmond Hill, where she was hired to work for a wealthy Scottish gentleman named Mr. Kinnear. Grace worked alongside two other servants: Nancy Montgomery, the housekeeper, and James McDermott, the stable hand. Tensions ran high among the three servants, particularly between Nancy and Grace. Nancy, who was sleeping with Mr. Kinnear, felt increasingly worried that her employer would turn his affections toward Grace. At the height of hostilities, while Mr. Kinnear was away in Toronto, Nancy fired both Grace and McDermott. McDermott decided to kill Nancy, and, though Grace tried to convince him not to, he did so. Then, when Mr. Kinnear returned, McDermott killed him too. When Grace gets to this part of her narrative, she still can’t remember any details about the murders.

Dr. Jordan listens to Grace’s narrative over the course of many sessions during his stay in Kingston, and the more he listens to her story, the more unsure he becomes about whether or not Grace is telling him the truth. He suspects that her amnesia is genuine, but he can’t shake the idea that she is some kind of mastermind who has carefully manipulated him with fictions and partial truths. As his confusion grows, he worries about his own loss of sanity. He has frequent sexual fantasies—some involving Grace—that come to him involuntarily and grow increasingly violent. Eventually the line between fantasy and reality blurs, and he begins a disturbing sexual relationship with his lonely landlady, Mrs. Humphrey. Unsure what else to do, Dr. Jordan allows a man named Dr. DuPont to hypnotize Grace. While under hypnosis, Grace speaks in an unusual voice and communicates in an uncharacteristically frank manner. Dr. Jordan guesses that this voice belongs to Mary Whitney. The voice confirms his guess, then goes on to say that she assisted McDermott in the murders and that Grace took no part in them. More confused than ever, Dr. Jordan abruptly leaves Kingston, never to return.

Grace remains in prison for an additional thirteen years before securing a pardon. Now forty-six years old, she travels to Ithaca, New York, in the United States. There, she marries a man named Jamie Walsh, whom she knew when she worked at Richmond Hill. He had testified against her during her trial, but he now believes Grace innocent and begs her forgiveness. The novel ends with Grace on the verandah of her new home, sewing a quilt that will include patches of material she’s saved from Mary Whitney’s petticoat, her own prison nightdress, and the dress Nancy wore when Grace first came to Mr. Kinnear’s. Stitched together in this way, the three women “will all be together.”