"Sarah's Key" is a historical novel by Tatiana de Rosnay that intertwines two narratives. One story follows a young Jewish girl named Sarah during the Vel' d'Hiv Roundup in 1942, when she is taken from her home in Paris with her family. In a desperate attempt to protect her younger brother, she locks him in a cupboard, believing she will return for him. The second narrative takes place in 2002, focusing on Julia Jarmond, an American journalist investigating the roundup. As she uncovers the truth about Sarah's fate, Julia becomes deeply connected to Sarah's story, leading her to confront the impact of the past on the present.