The Nightingale begins with an unnamed narrator looking at some old objects in her attic that date back to World War II. It is currently 1995, and the narrator lives on the Oregon Coast. Her son, Julien Mauriac, asks her about the objects, but she is evasive. Suddenly, the novel goes back in time to August 1939. The setting is Carriveau, France, a provincial town, where Vianne Mauriac lives with her husband, Antoine, and her daughter, Sophie. Although they live an idyllic life, Vianne and Antoine are worried because war is on the horizon. Vianne’s father, Julien Rossignol, fought in World War I, and she knows what war can do to the human soul. Vianne is now estranged from her father because of how the war impacted him. Eventually, Antoine is called to fight, and Vianne is left home alone with Sophie.
Meanwhile, Vianne’s younger sister, Isabelle, gets kicked out of her third school and is forced to return to Paris to live with her father. On the train to Paris, Isabelle is nervous, fearing that her father might not accept her. Although Julien takes Isabelle in temporarily, it is clear that he does not want to. A few months later, the Nazis invade France. Before they can make it to Paris, Julien sends Isabelle out of the city to go live with Vianne. Although Isabelle protests, she does as she is told.
Isabelle’s journey to Carriveau is perilous. Many people are fleeing Paris, and she is forced to walk most of the way on foot. On the way, she meets a handsome young man named Gaëtan who has just been released from jail. Gaëtan implies that he was jailed because he is a communist rebel. Isabelle immediately falls in love with Gaëtan, and they travel together to Carriveau. Although Gaëtan promises to take Isabelle with him to join the resistance after they stop in Carriveau, he instead leaves Isabelle behind with a note that says, “You are not ready.”
Although Vianne is happy to see her sister safe, their relationship is strained. Vianne feels guilty that she was not there for Isabelle after their mother died and their father virtually abandoned them. Vianne’s life becomes even more complicated when a German soldier, Beck, is assigned to live in her home. Isabelle treats Beck—and any other German she meets—rudely, and Vianne worries that she will put Sophie’s life in danger.
Isabelle continues her rebellious streak by joining the local resistance. In the night, she secretly passes out flyers that contain anti-German sentiments. Eventually the resistance asks her to travel to Paris to deliver a message and act as a point of contact. Before departing, she lies to Vianne and says she is leaving to be with a boy. Vianne believes Isabelle and chastises her for her seemingly irresponsible actions. Once in Paris, Isabelle convinces Julien to let her live with him.
Vianne’s life with Beck is mostly comfortable. Although he is a German soldier, Vianne thinks that he is a good man. He treats her and Sophie with kindness and respects their property. Additionally, he does Vianne a favor and looks into Antoine’s status. As it turns out, Antoine is in a POW camp and isn’t allowed to come home. One day, Beck asks Vianne to write down the names of all the Jewish people who teach at Vianne’s school. Vianne is hesitant but ultimately does what Beck asks because he promises to send Julien a care package. The list gets Vianne’s best friend, Rachel, fired from her job for the crime of being Jewish. Vianne angrily confronts Beck who tells her that he did not know what the list would be used for and that he was just following orders. Vianne is unsure whether to believe him.
For some time, Vianne has a difficult time trusting Beck. However, one day, while Vianne is with Rachel, Beck shows up and tells them to make sure that Rachel cannot be found the following day. His implication is that something will happen to her because she is Jewish. Vianne trusts Beck. That night, she attempts to take Rachel and her children, Sarah and Ari, to the Free Zone of France. However, while standing in line to pass through a checkpoint, a Nazi soldier begins firing into a crowd of people, and a stray bullet hits Sarah, killing her. Vianne, Rachel, and Ari flee back to Vianne’s home. Vianne recovers Sarah’s body and buries her while Rachel and Ari hide in a secret space Isabelle created below Vianne’s barn.
The next day, however, authorities show up and arrest Rachel and put her on a train headed for Germany. Rachel leaves Ari with Vianne. When Vianne returns home with Ari, Beck informs her that soon Ari won’t be safe either, but he promises to do what he can to help. Eventually, Beck manages to secure identity papers for Ari that say his name is Daniel. From that point on, Vianne raises Ari like her own son.
In Paris, Isabelle becomes a key figure in the resistance. She also learns that her father has been acting as a member of the resistance all along. In fact, he wrote the pamphlets she delivered all over Carriveau. Not long after arriving in Paris, Isabelle spearheads an effort to transport British fighter pilots across the Pyrenees and into Spain. Over time, she rescues dozens of pilots this way. Along the way, she picks up the code name “The Nightingale” and becomes a notorious figure among the Nazis. Additionally, she reunites with Gaëtan, who is also part of the Paris resistance.
One day, Isabelle returns to Carriveau for a resistance meeting. On her way to the meeting, she sees a fighter pilot go down and quickly moves to rescue him. She takes the pilot to Vianne’s barn and hides him in the secret space. Beck is put in charge of finding the down pilot and is frustrated when he cannot. While Beck is away, Vianne sees the barn door open, goes to investigate, and finds Isabelle and the fighter pilot. Vianne chastises Isabelle for putting her life and Sophie’s life in danger once again. Isabelle apologizes and promises to leave as soon as possible. Just then, Beck comes home and starts searching the property. Just before he checks the space in the barn, Vianne hits Beck in the head with a shovel, killing him. As she does so, Beck’s gun goes off and a bullet strikes Isabelle, wounding her. Immediately after, Gaëtan shows up to help. He promises Vianne to get rid of the bodies and help Isabelle.
Gaëtan gets rid of the bodies and nurses Isabelle back to health. While acting as Isabelle’s nurse, Gaëtan and Isabelle fall in love and begin a sexual relationship. However, after a few weeks of romance, Gaëtan goes to join a group engaging in guerilla warfare, and Isabelle returns to escorting pilots. Not long after, Nazis capture and torture Isabelle. They want to know the identity of “The Nightingale,” which Isabelle refuses to give up. Julien, wanting to protect his daughter, turns himself in to the Nazis, claiming that he’s the Nightingale. The Nazis execute Julien in front of Isabelle and then ship her to a labor camp in Germany.
Meanwhile, a new Nazi, Von Richter, moves into Vianne’s house. Von Richter is a savage who is cruel to Vianne and her children. Vianne increasingly worries for her family’s safety. One day, Vianne sees a Jewish woman being shepherded onto a train with her child. The woman gives Vianne her child and asks her to save him. Vianne takes the child to her local church leader, whom she trusts, and begs her for help. Mother Superior, the church leader, promises to help Vianne, and together they secure identity papers for the child and keep him safe. At this point, Vianne becomes an active part of the resistance and starts helping numerous children in similar ways, all with help of Mother Superior.
One day, Vianne comes home and finds Von Richter with a horrifying smile on his face. He tells Vianne that he knows Ari’s true identity and asks her what she will do to keep that information from getting out. Vianne tells him that she will do anything, and so he rapes her. Von Richter repeatedly rapes and abuses Vianne; months later, she discovers she is pregnant. Not long after, the German troops pull out of Carriveau, and Antoine returns home having escaped from the camp he was held in. Vianne decides to have sex with Antoine right away and pretend that the child is his.
While Vianne is dealing with Von Richter and her pregnancy, Isabelle struggles to survive in a labor camp. She manages to survive until American troops come and liberate the camp. She returns home to Carriveau a sick and broken woman. Vianne cares for Isabelle the best she can, although it is clear that Isabelle will soon die. Before Isabelle dies, Gaëtan returns to Carriveau and sees her one last time. Isabelle dies in his arms.
The novel ends with the unnamed narrator from the beginning attending a reunion in Paris. The novel reveals that the narrator is Vianne, and she is attending the reunion on behalf of Isabelle, and many fighter pilots who Isabelle saved as well as their families attend the event. Gaëtan is also there, as is Ari, who moved to America to live with his relatives after the war. Vianne attends the conference with her son, Julien (who is actually Von Richter’s child). Although Julien learns a lot about his mother’s past at the conference, Vianne never tells him who his real father is—that is one secret she wants to keep hidden.
