Eight years after they overthrew Churchill and led Britain into a separate peace with Hitler, the upper-crust families of the "Farthing set" are gathered for a weekend retreat. Among them is estranged Farthing scion Lucy Kahn, who can't understand why her and her husband David's presence was so forcefully requested. Then the country-house idyll is interrupted when the eminent Sir James Thirkie is found murdered - with a yellow Star of David pinned to his chest.
Lucy begins to realize that her Jewish husband is about to be framed for the crime - an outcome that would be convenient for altogether too many of the various political machinations underway in Parliament in the coming week. But whoever's behind the murder, and the frame-up, didn't reckon on the principal investigator from Scotland Yard being a man with very private reasons for sympathizing with outcasts and underdogs - and prone to look beyond the obvious as a result.
As the trap slowly shuts on Lucy and David, they begin to see a way out - a way fraught with peril in a darkening world.