In the year 1942, a young Scot named Charlotte Gray embarks on a journey to London, seeking a position as a medical receptionist for a prestigious Harley Street physician. During her train ride, she encounters a man who engages her in conversation and hands her a card detailing a forthcoming book launch. Despite the surrounding turmoil of war, the vibrant social life of London thrives, prompting her friends to persuade her to attend the event. At the gathering, she crosses paths with Flight Lieutenant Peter Gregory, only to be interrupted by the same man from the train, who insists she meet influential figures.
The fleeting nature of life during wartime becomes apparent as Charlotte quickly finds herself falling for Peter. Their conversations explore themes of war and valor, where she expresses her belief that she is being recruited for a covert organization. However, Peter, cautious of her involvement, advises her against it, as he prepares for his mission over France in the days to come.
Driven by her desire to contribute, Charlotte enlists in the Special Operations Executive (SOE) and is assigned to the First Aid Nursing Yeomanry (FANY) with the title of Driver. After undergoing rigorous training, she receives devastating news: Gregory's aircraft has been shot down, and he is now classified as missing in action. With a childhood spent in France and fluency in the language, Charlotte's skills are recognized, leading her to sign up for dangerous missions within France.
Upon being dropped into the country with two comrades, Charlotte's initial assignment involves a risky test run—a transfer of crucial radio components. However, the threat of exposure looms, prompting her to adopt the role of housekeeper for an aging, uninspired artist named Levade, who happens to be the father of her main contact in the resistance, Julien. As her mission unfolds, Charlotte also takes refuge in hiding two Hebrew boys, Andre and Jacob, following the arrest and deportation of their parents. The story unfolds amidst the growing atrocities faced by the Hebrew community in France, further compounded by the complacency of the Vichy French authorities.
As the narrative progresses, Levade is questioned about his Hebrew lineage. When he chooses silence, Julien courageously reveals their shared ancestry to protect the boys. Subsequently, Levade is unjustly sent to a prison camp, while Julien is spared, deemed insufficiently Hebrew by the law. However, betrayal by the duplicitous schoolmaster Renech results in the boys' capture. In a poignant moment, Charlotte pens a heartfelt letter to them, signing it as their mother, and desperately attempts to deliver it through a small gap in the train cargo box, where they share space with Julien's father and others saying their goodbyes.
In the war's aftermath, Charlotte Gray finds herself reunited with the now-Squadron Leader Peter Gregory. She reveals her profound grief since the moment she believed him lost. The film culminates with Charlotte’s return to France and to Julien, while it leaves the fates of Julien's father and the two boys shrouded in uncertainty. However, the source material clarifies the tragic end met by all three in the concentration camp, compelling the audience to reflect on the devastating consequences of war.
