This novel, a blend of coming of age narrative and espionage thriller, tells the story of Leonard Marnham, a young British postal worker and unexpected government agent in Berlin in the months following the end of World War II. As he finds himself caught up in a web of tensions spun between the American and British allies, he also discovers the joys of love and sexuality, with the two aspects of his life coming together in a horrific and intense climax. Both these narrative lines are, on some level, defined by the narrative's examination of the complex relationships between conquered and conqueror.

The narrative begins shortly after Marnham's arrival in Berlin. After receiving a series of orders, first from a British contact and then from his American supervisor, Bob Glass, Marnham finds himself assigned on a top secret surveillance project, headquartered in a secret facility outside Berlin and co-sponsored by the American and British intelligence agencies. The night before he is due to officially start work, Glass takes Marnham out to a succession of nightclubs, where he gets increasingly drunk and encounters the attractive Maria, a German woman with whom he quickly and irreversibly becomes attracted.

As he becomes absorbed into his dull and repetitive nature job, Marnham becomes obsessed with thoughts of Maria, eventually putting together a plan to meet her. As he puts that plan into effect, he unexpectedly encounters Maria herself in a meeting that results in his being seduced into a relationship that opens him up both emotionally and sexually. Over the next few weeks, Marnham finds that his job is becoming less and less important to him even when he receives a secret assignment from a British superior.

One day when he returns home from work, Marnham is shocked to find that Maria has been assaulted by her ex-husband Otto. As they struggle to recover from this invasion of their happiness, they also respond fearfully to the threat of a return visit. Eventually however, and after Marnham returns briefly to England where he realizes how much he wants to be with Maria, they put their fears aside and agree to marry. At their engagement party, after Glass gives a sentimental speech, Marnham is warned by a new downstairs neighbor that Glass's espionage activities are well known and that to keep himself and his life safe and quiet, he should be careful about how much they associate. Later, after a late dinner out, Marnham and Maria discover that Otto has invaded Maria's apartment. A violent confrontation results in Marnham killing Otto in self-defense. His conversation with Maria in the aftermath of Otto's death makes Marnham realize they have no choice but to dispose of the body and the narrative graphically describes how the two lovers cut up the body and load it into a pair of suitcases for disposal.

A complicated chain of events, including Marnham's repeatedly frustrated efforts to dispose of the suitcases and their contents, results in the cases being stored in the basement of the secret research facility. Shortly after he leaves the suitcases, Marnham is shocked to learn that the facility is being raided by the Russians and worries that Otto's body is going to be found, leading the authorities back to him. As it turns out, however, Marnham faces no reaction to the bodies being found and is reassigned back to Britain. Maria says goodbye at the airport, promising to visit him as soon as she can. As he is boarding his plane, however, Marnham sees her on the airport roof with Glass's arm around her shoulder.

The book's final chapter, set thirty years after the events of the rest of the book, finds Marnham back in Berlin for the first time since he left. As he walks through familiar streets and unfamiliar buildings, he remembers the past and contemplates the future. This is a response to a letter from Maria explaining her feelings, what happened between her and Glass, and expressing the hope that she and Marnham can someday, somehow recapture what was special between them. The novel concludes with Marnham resolving to bring Maria back to Berlin and rebuild their relationship.