1946 London. One evening, novelist Maurice Bendrix runs into his old friend, mild-mannered government minister Henry Miles, who he has not seen in two years. Maurice met Henry and his wife Sarah Miles in 1939 when they were neighbors off the Common, Maurice using the notion of Henry as research for a character for one of his novels. The reason they have not seen each other in such a long time is that last meeting is when Sarah, without warning, abruptly ended her affair with Maurice, an affair of which Henry had and has no knowledge. This meeting at least brings Maurice back into the Miles' realm and again seeing Sarah. Maurice is as dismayed to hear as Henry is dismayed to tell that he believes Sarah currently is having an affair. Beyond still being in love with her, the deeper reason for Maurice's dismay is not only Sarah having professed her eternal love for him during the time they were together, but her vow that she would never sleep with another man, her and Henry's marriage, while one of emotional need, not of romantic love or sex. Stemming from a conversation between the two men, Maurice employs a detective agency to discover the nature of what Henry believes is Sarah's affair. In the process of discovering what Sarah has been doing, Maurice may discover what happened to end their affair and if she has been true to her word of her eternal love and sexual faithfulness to him.