Muriel Spark’s novel centers on aging and death among a circle of relatives, lovers, friends, and acquaintances. One unifying factor is that many characters receive mysterious phone calls that are thinly disguised death threats, with the caller stating “Remember, you must die.” The book is not, however, a conventional mystery story: while every person who receives the calls does die during the course of the novel, the identity of the caller is never revealed.

Lettie Colston is among the first to receive such a call. She and her brother, Godfrey, share a house with Godfrey’s wife, Charmian, who is recovering from a stroke that has affected her mentally and physically. Lettie reports the call to the police; at first it does not bother her, but she gradually becomes obsessed. Godfrey, although concerned with Charmian’s care, is often lost in sexual fantasies and fetishes.

His former lover, Lisa Brooke, has recently died, and several characters attend her funeral. These include her ostensible husband, Guy Leet, who is Charmian’s former lover; later he learns that Lisa had a previous marriage, so theirs was not legal. Lettie convinces Godfrey to hire Lisa’s former housekeeper to assist with Charmian’s care. This proves a bad move, as Mrs. Pettigrew transfers her blackmailing schemes from Lisa, with whom she had some success, to Godfrey. The Colstons ignore the warnings of Jean Taylor, Charmian’s former companion, who lives in a nursing home.

Alec Warner, Jean’s one-time lover, also receives a “remember” call, and soon Godfrey and Charmian receive them as well. Retired police inspector Mortimer, to whom they have reported them, becomes concerned. He invites them all to his home to discuss the situation but offers little practical advice. He does not reveal that he receives the calls as well and attributes them to Death itself.

Jean and Alec communicate the secrets about the long-ago affairs to the people involved so that Mrs. Pettigrew cannot blackmail Godfrey. A burglar surprises and kills Lettie in her home; the investigation of the murder helps reveal Lisa’s former marriage. Her real husband, an institutionalized mentally ill man, later dies, leaving Mrs. Pettigrew her beneficiary. As Charmian recovers her mental faculties, she opts to leave Godfrey and live in a long-term care facility.