The film is an adaptation of a 1938 stage play by John Boynton Priestley. It is set in Edwardian-era Yorkshire, where three married couples gather to celebrate their Silver Wedding Anniversary (25th Anniversary). They were all wed on the same day, a quarter century ago. To their surprise, they learn that a legal technicality may render all three marriages invalid. Meaning that they have been "living in sin" for 25 years. Following their initial shock, they start contemplating single life. Some of them are fed up with their spouse, others remember past love interests who they have not seen in a long time. And yet others are trying to get reacquainted with their spouse.