The novel The Nightingale revolves around the lives of two sisters, Vianne Mauriac and Isabelle Rossignol, in France during World War II. Rossignol (Also Vianne's maiden name) means 'nightingale' in French and is used later in the book as the code name for Isabelle. Although they are sisters, their personalities and interests could not be more different. Vianne originally wants only to keep her daughter safe and maintain the status quo while awaiting the return of her husband from the front lines while Isabelle cannot sit still and is eager to join the resistance and fight in any way she can. Both sisters end up becoming heroes of France and of the Jewish community in completely different ways.

While Vianne and Isabelle are the main characters, there are a few other major characters that greatly impact the decisions the sisters make. Sophie, Vianne's daughter, grows up during the German occupation of France. Many of Vianne's decisions are to protect her daughter. Captain Wolfgang Beck is the first of two German officers given orders to stay at Vienne's house. Captain Beck is kind, well-mannered, and honorable, making sure that Sophie has enough to eat once he realizes that Vianne has been starving herself to feed her and warning Vianne when the Jews are to be deported. Rachel has been Vianne's best friend since childhood and is Jewish. When she is rounded up with the rest of the area's Jewish population after a failed escape attempt resulting in her daughter's death, she begs Vianne to take her son and raise him. This move sparks what would be Vianne's greatest contribution during the war. For Isabelle, the greatest influence is a man named Gaëtan, who not only helps Isabelle survive the journey away from Paris to her sister's house during German attacks, but is later instrumental in getting her into the resistance.