Working as a courier for an escape line over the Pyrenees early in the Second World War, Françoise is approached by the British Secret Service. Is what they propose - involving leaving her family and entering the lethal game of wartime espionage - reasonable for a young woman only two years after finishing her schooldays in Bordeaux? Françoise's best friend, Justine, enters the glamorous world of haute couture, which is still thriving in occupied Paris. Justine has a past that, should it be discovered, could mean deportation to the camps in Eastern Europe. Justine's sister, Claudia, a brilliant mathematician working in Berlin on a top-secret project for the German High Command, is faced with the nightmare of betraying her country if she is to save her life. Powerful and emotional, the close relationships between Françoise, Justine and Claudia are tested by their conflicting wartime allegiances as they struggle to take possession of a secret that can alter the course of the war...