Sarah is 10 on that July 1942 night when the French gendarmes knock on the door of her Paris apartment. They have come to take her family to the velodrome where they and all the Parisian Jews will wait 3 or 4 days with little or no food and water. Eventually the Jews are sent to a camp outside Paris from where they will be transported to the German death camps.
When the police came Sarah hid her brother in a locked cupboard, naively believing she would return for him the next day. She places the key to the cupboard in the pocket of her dress.
At the camp outside of Paris she is separated from her parents and eventually escapes and is befriended by an elderly French couple. They help her get back to Paris and to her former apartment.
The story moves back and forth between 1942 France and 2002 France. This part of the story is told by Julia Jarmond an American expat and journalist who is married to a Frenchman, Bertrand. They have one child and are preparing to move into the apartment occupied by Bertrand's grandparents and father shortly after Sarah's family was removed.
Julia has been assigned by her newspaper to write about the 60th anniversary of the removal of the Jews from Paris. In the course of her investigation she learns the apartment she is preparing to move into was that of a Jewish family. She learns their identity and begins a search for them. She also learns a dark secret hidden by her husband's grandmother and father.
Sarah's Key is, like most stories of the Jews during WWII, disturbing and horrifying. Yet it is also a story of redemption and ultimately is an affirming account of one woman's journey to bring closure to Sarah's remaining family.