The book tells the story of two sisters in France during World War II and their struggle to survive and resist the German occupation there.

The book was inspired by accounts of a Belgian woman, Andrée de Jongh, who helped downed Allied pilots escape Nazi territory.

However, the main action of the book is told in third-person, following two sisters, Vianne Mauriac and Isabelle Rossignol, who live in France around 1939, on the eve of World War II.

Vianne, the eldest sister, is a married schoolteacher raising her 8-year-old daughter Sophie in her childhood home named Le Jardin in the town of Carriveau.

At home, Vianne copes with the occupation of France after defeat by the Germans, and struggles to keep her and her daughter surviving in the face of poor food rations, the loss of her job, and dwindling money left behind by Antoine.

After being expelled from finishing school, she travels from Paris to Carriveau on foot, meeting a young rebel named Gaëtan Dubois along the way.

After moving to a cell in Paris, she develops a plan to help downed Allied airmen escape to the British embassy in neutral Spain, from where they can be repatriated.

She is successful, and with support from other Resistance operators (including her father, with whom she begins to rebuild a relationship) and the British MI9, this becomes her primary task throughout the war.

De Jongh was captured late in the war and sent to the Ravensbrück concentration camp; the Nazis did not execute her because they did not believe that she had organized the escape route.

[10][11] The book was optioned in March 2015 by TriStar Pictures for screen adaptation, with Ann Peacock to write and Elizabeth Cantillon to produce.

[18] Initially principal photography was set to begin on October 26, 2020, with scenes to be shot in Budapest, Hungary and Los Angeles, California,[19] but less than a week before shooting was to commence, the start of production was delayed because of the pandemic.

[22] In September 2021, Laurent commented on the film's status and the delayed production, "It's super hard for us to find another date and to make everybody on board at the same time, so it's a mess.