The protagonist of the novel is Barbara, an older unmarried history teacher. She is a very lonely individual and wishes she could have a friend to share her time with. She reveals that her last friendship with Jennifer Dodd, ended badly with Dodd stating she will take an injunction against her if he tries to contact her again.
Sheba is a new and younger art teacher at the school that Barbara works at. Barbara quickly becomes friends with Sheba and begins to structure her life around the friendship. Sheba, on the other hand, has begun to start flirting with a student, Steven Connolly, and soon after begins an affair with him.
Sheba confides in Barbara that Connolly has made advances towards her, but she does not reveal the extent of their relationship. Sheba also states that her marriage has been in difficulty. She reveals that she married young to an older man, Richard, and is now facing problems with her rebellious teenage daughter, Polly.
Barbara later learns of how far the affair has carried on when she spots Sheba and Connolly speaking to each other. She is hurt and angry that Sheba did not trust her enough to tell her. Later on, Barbara feels further betrayal when her cat develops cancer and Sheba leaves her in distress because she wants to meet Connolly.
Sheba becomes infatuated with Connolly and her obsession grows so much that she begins to write him love letters. However, Connolly’s infatuation with her begins to decline and soon he begins to try to get rid off her.
Another teacher, Brian, invites Barbara to lunch one day. Initially, Barbara is overjoyed because someone finally likes her, but then realizes that Brian only invited her because he wants to learn more about Sheba. Barbara’s anger intensifies and she strongly hints to him about Sheba’s relationship with Connolly.
Sheba’s home life has become further strained, and her daughter accuses her of having an affair. Sheba is distraught and looks to Connolly for comfort, but when she turns up at his house, she learns that he is now in a relationship with another younger girl.
Sheba is suspended from her job after Bangs informs the school about the affair. Richard is angry and throws her out of their home. Polly’s accusations were proved to be correct and she refuses to accept her mother’s apologies. Sheba is now alone and she and Barbara move in together.
Later, Sheba finds Barbara’s diary detailing all of Sheba’s life events. Sheba is initially angry at how Barbara has managed to make out as if she was present during the encounters with Connolly. However, Sheba has lost everything and clings to Barbara, just as Barbara always wanted.
