Grace Angel is the novel’s protagonist and first-person narrator, narrating the “Present” chapters in the present tense, and the “Past” chapters in the past tense. She begins Behind Closed Doors as a successful woman in her early thirties who has a job selling fruit for Harrod’s. On top of that, she has the responsibility of taking care of her sister, Millie, who has Down Syndrome. Those two things have left her little time for love, and, in fact, when she has been in a relationship, her partner has been turned off by the idea that Millie will eventually graduate from school and come to live with them, as Grace is her sole guardian. However, when she meets Jack, everything changes. He seems delighted with Millie, and Grace falls in love with him.

Unfortunately, Jack is not at all who he seems. Though he begins to take control of her life under the guise of caring—encouraging her to quit her job so they can have children more quickly, becoming co-guardian of Millie, and buying her a beautiful home—all of these gestures turn out to be a way for Jack to imprison Grace in her new house and leave her without options for escape.