A diplomat's daughter, Marian Sutro is an outsider - half French, half British. When she is recruited by SOE, her hybrid status and fluent French will be of service for her to go undercover in wartime France on a dangerous cause. Trained in sabotage, dead-drops, how to perform under interrogation and how to kill, Marian parachutes into south-west France - officially as a Resistance courier. But her real destination is Paris, where she must find Clement Pelletier, a family friend, once the focus of her adolescent desires. A nuclear physicist, Pelletier is engaged in the race for a new and terrifying weapon and of urgent significance to her superiors. Marian struggles towards this reunion, understanding that war changes everything, and neither love nor fatherland may be trusted.