Set in London, England, and Ireland during World War II, Elizabeth Bowen’s novel is concerned with the moral and ethical dilemmas that people face during wartime. Stella Rodney lives in the bombed-out city, contributing to the war effort and earning a living doing coding for military intelligence. Widowed and with an adult son, Roderick, she also has a lover, Robert Kelway. She believes he is a British officer on a secret assignment, but her world is shattered when she is told otherwise. When Robert Harrison, a British intelligence officer, tells her that Kelway is a Nazi spy, she is at first incredulous. She must decide if this is true and what her proper course of action should be.

The novel opens with Harrison sitting on a park bench listening to a concert, waiting for the time of his appointment to pay a visit nearby. Louie Lewis, a poorly dressed woman, tries to initiate conversation, but he rebuffs her. She gives the impression of having an intellectual disability. Harrison then goes to Stella’s flat. She had been thinking about Harrison, whom she has known for a few weeks, and wondering why he was so persistent in his attention to her. After he arrives, he soon tells her an amazing story: Kelway is not, as she believes, a loyal officer, but a Nazi sympathizer who is passing secrets to the Germans. Harrison demands that she leave Kelway and begin an affair with him; otherwise he will turn her lover in.

Stella gets his agreement for some time to think this over, and she then turns her attentions to her son, who is in the army but home for a few days. Her cousin has recently died and left a home in Ireland to Roderick, which he is interested in seeing soon to plan its restoration. A few days later, Roderick goes back to duty, and Kelway arrives. They soon go to visit his family at their country home. When she returns, Harrison turns up, verifying that he has her under surveillance. Stella briefly goes to Ireland to see her son’s inheritance.

Back in London, Stella confronts Kelway with Harrison’s information, which he staunchly denies. He also proposes marriage, but she defers replying. A few days later, dining out with Harrison, Louie approaches and interrupts them. After Harrison leaves, the two women have a conversation. Stella has by now decided to agree to Harrison’s terms. When Kelway comes to her apartment the next night, after they make love, he reveals that the story is true: he is a Nazi. Hearing noises outside, he flees through the skylight onto the roof. The next day, his dead body is found in the street below.

More than a year later, after the Allied victory in Italy, Harrison turns up again, but questioning him seems futile. Stella is already engaged to marry another man.