Sarah’s key, from which the novel takes its title, symbolizes two things. First, it symbolizes the struggle of one little girl to save her brother. Second, it symbolizes the failure of those in France to refuse to obey the orders that led to Michel’s death. Ultimately, his life and death are beyond her control. The key, then, both opens and closes life for Sarah. 

This is what Julia is frequently referred to as in the novel. She struggles with her inability to truly become Parisian and recognizes that she’ll always remain an American to them. This tension comes to a head with her husband, Bertrand, who resents her ideals and truth seeking as American interference. Eventually, Julia returns to the USA, but feels that Paris might always be her real home. 

Mamé’s apartment on the Rue de Saintonge contains a history deeper than Julia could have been prepared for, and one that is deeper than the Tézac family would have liked to be revealed. The apartment comes to symbolize loss—the loss of Sarah’s home and brother. It’s clear that no one wants to live in it after learning of the events.