The novel opens in the midst of World War II, in a London park where a concert is taking place. Present at the concert are Louie, a young woman whose husband is fighting in the war, and Harrison, an English counterspy. Louie attempts to flirt with Harrison, who sternly rebuffs her. After the concert, Harrison goes to the flat rented by Stella Rodney, a middle-aged woman who works for the government. Harrison is in love with Stella and has been pursuing her for years; Stella is in love with another man, Robert Kelway. Harrison now tells Stella of his suspicions that Robert is a spy for the German government. He promises not to report Robert to the government if she leaves Robert to become his lover.
Stella rejects Harrison's offer but considers the possibilities. Her son, Roderick, visits her on leave from his army training. The novel recounts how Roderick had inherited Mount Morris, the Irish estate owned by his father's cousin Francis. An elderly and wealthy man, Francis had died while visiting his wife, Nettie, at a home for the mentally infirm. It was at Francis's funeral that Stella first met Harrison, who claimed to be a friend of Francis.
Stella continues her relationship with Robert, meeting his eccentric family and holding off Harrison. She eventually leaves for Ireland to visit Mount Morris and take care of affairs for Roderick. Her time there reminds her of her youth, when she had been married to Roderick's father; they were later divorced. Stella resolves to ask Robert about Harrison's allegations. In England, Robert denies the accusations, upbraiding Stella for distrusting him. He then proposes that they get married.
Roderick visits his cousin Nettie to learn whether she wants to return to Mount Morris. Nettie displays a surprisingly sound presence of mind, revealing that she has feigned mental illness to live life on her own terms. She also tells Roderick that, contrary to universal belief, Stella had not initiated her divorce. Roderick's father had begun the proceedings after he fell in love with an army nurse. Roderick confronts his mother with this information, to which she responds that everyone has always assumed she was the guilty party. A phone call from Harrison interrupts the conversation, and Stella accepts his dinner invitation to avoid her son.
At dinner, a startled Stella talks with Harrison about her past. She admits that she lied about her role in the divorce to prevent other people from thinking of her as her husband's fool. Harrison reveals that he knows Stella told Robert about him. He tells her that he now has to arrest Robert. Before Stella can respond, Louie notices Harrison and interrupts their conversation. Stella uses the opportunity to indirectly mock Harrison. She seems to hurt his feelings, and when she implicitly offers to have sex with him to prolong Robert's life, he declines.
Robert gradually becomes aware that the government is converging on him. He goes to Stella to confess his lies. He admits that he spies for Nazi Germany, explaining that freedom provides humanity with nothing but an opportunity to destroy itself. Stella is repelled by his beliefs but she loves him too much to abandon him. Robert tells her that he must leave before they learn to hate each other. He kills himself by throwing himself from the roof of Stella's building.
The narrative gives a sweeping overview of the next two years of the war. Roderick decides never to learn more about his father, instead resolving to live peacefully at Mount Morris. Harrison visits Stella again during another bombing, where she seems to let him down gently. He tells her that his first name is Robert; the resolution of their relationship is left ambiguous. Louie gets pregnant in the course of her extramarital affairs but her husband is killed in action without knowing. Louie leaves London to give birth to her son. She retires with him to her home town, with the intent to raise him as if he were her heroic husband's child.
