After walking for two days, Marie-Laure and her father reach the museum director’s friend’s home in Evereux, only to find it burning and being looted. The town is in a state of chaos. The owner of the home has fled to London, leaving her father responsible for the diamond. They sleep in a nearby barn. Now they must go to Saint-Malo.

Werner travels to Essen to take the entrance exam for the National Political Institutes of Education. Most of the boys in his age group are bigger than he is. Most of the boys are blond and all have blue eyes. Even so, Werner stands out with his shock of white-blond hair. The boys are tested physically and academically, over eight days. Werner is certain that he will not be chosen because he is not physically strong. All the boys desperately want to be chosen.

One test terrifies most of the boys. They must climb a ladder 25 feet in the air and jump off, landing in a flag held by the rest of the boys. The first boy is dropped, landing on his arms, both of which are broken. Others are injured or refuse to jump. Werner steels himself. When it is his turn, he climbs and jumps without hesitation.

A truck offers Daniel, Marie-Laure and other refugees a ride most of the way to Saint-Malo. They walk the rest of the way. At times, Daniel carries Marie-Laure on his back. Daniel reassures her that the sound she hears is the ocean, not an army approaching. Finally, they reach her uncle’s house in the ancient walled city on the sea.

The housekeeper, Madame Manec, lets them in and feeds them. As Daniel and Madame Manec talk and smoke cigarettes, Marie-Laure falls asleep at the table.

Werner is accepted into the national school at Schulpforta. He is to report there in two weeks. The neighborhood celebrates Werner’s acceptance. Jutta will not speak to him.

Safe in her great-uncle’s house in Saint-Malo under the care of Madame Manec, Marie-Laure wakes to the sound of the ocean. Madame Manec tells her that her great-uncle came back from World War I a changed man; he never leaves the house, and frequently stays in his room for days on end. After being gassed and seeing the horrors of war, Etienne sees things that are not there. However, he is an educated, sensitive, and intelligent man.

The radio broadcasts are dominated by people looking for family and friends they have lost in the confusion of occupation. Marie-Laure and her father share a bedroom on the sixth floor of this tall, narrow house.

Werner’s last days before he is to report to Schulpforta tick down. Jutta is still avoiding him, but on his last day at home, he asks her to go for a walk with him. She tells him that he will turn into a Nazi if he goes to Schulpforta, committing atrocities like the ones she heard about on the radio as Germany invaded France. Though she is only 12 years old, she tells Werner that he is wrong to do something simply because everyone else is doing it. He feels that he has no choice but to go: He does not want to go down into the mines, and the unknown cruelties of the Nazi school pale in comparison to his fears of the mine.

When he tries to paint a pretty picture of what they will be able to do when he graduates from the school, even tempting her with a trip to Paris, Jutta tells him not to lie to her.

On her fourth day in the house, Marie-Laure wakes to find a trail of seashells leading to her uncle’s door on the fifth floor. He welcomes her and shows her his 11 radios, several of which he built himself. His voice is soft and reminds her of silk. His room is a wonderland of switches, pieces of electronics, shells, and books. He reads to her from Darwin’s The Voyage of the Beagle, translating from English into French as he reads. To Marie-Laure, he seems completely sane.

Marie-Laure’s father goes out into the village to witness the arrival of the Germans, who sweep into town and are greeted by the mayor. Soon the Nazi flag is unfurled from the window of the Château de Saint-Malo.

Werner’s school building is a castle from a fairy tale. There are 400 boys, ranging in age from 9 to 17, attending the school. They all have blue eyes, and they are not allowed personal possessions. They are to live only for duty to their country.

Werner sleeps in a dormitory with seven other 14-year-olds. Werner makes a friend, Frederick, whose father is an assistant to an ambassador in Berlin. Frederick is an expert in birds. Werner, along with the other boys, yearns to belong to this school and to fulfill its ideal of manly sacrifice.

Sergeant Major Reinhardt von Rumpel travels through German-occupied Europe confiscating antiques, jewels, paintings, and other precious objects on behalf of the Reich. Currently in Vienna, Von Rumpel reads about the Sea of Flames—a blue diamond with a red center—in a 400-year-old manuscript and determines to find it. He has a strange, uncomfortable lump in his groin.

The town of Saint-Malo endures the occupation: all music, dances, and public meetings have been banned. A curfew is put in place. The neighbors all come to see Madame Manec and tell her the news. Madame spoils Marie-Laure with chocolate, lemonade, and wonderful meals. Etienne reads to her one day and the next hides in his room with a headache. Marie-Laure’s father tells her they will leave Saint-Malo as soon as he hears from the museum director in Paris. Weeks pass and they hear nothing.

Dr. Hauptmann, Werner’s science instructor, gives each boy in his class a kit and tells them they have one hour to construct a circuit, then a simple motor. Werner accomplishes each task easily. He is the only boy in the class who does.

The Germans order all citizens to turn in their firearms: anyone keeping a gun will be shot. Marie-Laure and Etienne imagine traveling to distant lands: Mozambique, Scotland, and New York City. Etienne’s couch becomes their magic carpet, on which they escape the reality around them.

Werner is summoned to Dr. Hauptmann’s office. Frank Volkheimer, a 17-year-old cadet, also known as the Giant, sits near the fire. Dr. Hauptmann tests Werner on a trigonometry formula to locate an unknown point using two known points. When he solves the equation, Dr. Hauptmann tells Werner that he will work in the professor’s laboratory every day after dinner. Volkheimer is assigned to Werner as a kind of bodyguard.

One day, when Etienne is suffering from a panic attack, Marie-Laure tries to distract him by asking him questions about her grandfather’s room and the attic. Etienne shows her the attic, which can only be reached through her grandfather’s room on the sixth floor. The attic is full of light, a gramophone, and a complex, powerful radio. Henri, Marie-Laure’s grandfather, and Etienne recorded children’s science lessons on gramophone records before the war, in which Henri died. It is Henri’s voice on the records, which Etienne now plays for Marie-Laure. He describes his war experiences as a signalman with Henri; lying in the trenches, exposed each night to the terrifying prospect of the German flares lighting the way for a sniper’s bullet. After the war, he played the records until they wore out, including a recording of Henri playing Debussy’s “Claire de Lune.”

The end of this chapter consists of three letters from Werner to his sister, Jutta. He tells her of his work with Dr. Hauptmann, his friendship with Frederick, and the protection offered by Volkheimer.

It is October in Saint-Malo, and Big Claude, the perfumer, capitalizes on the opportunities offered by the occupation. He pays local farmers to butcher rabbits and lambs; he then carries the meat to Paris and sells it, making a lot of money. He notices Marie-Laure’s father pacing off distances and scribbling notations in a notebook. He believes the German authorities will be very interested to know about LeBlanc’s activities.

Marie-Laure has still not been allowed outside the house, while her father works furiously on a model of the town for her. She begs to go outside, particularly to the ocean, but her father will not allow it.

Bastian, Schulpforta’s field commandant, tests the boys by forcing one boy to identify the weakest boy in the group. Then, he tells the weakest boy to run across the field, with a brief head start. If the weakest boy makes it across before the group catches him, he is safe. If not, he will be at the mercy of the mob of boys. Werner is terrified, because he is by far the smallest boy. However, another boy is chosen and survives by narrowly outrunning the mob.

Citizens of occupied France are required to surrender their radios. It takes Daniel several hours to carry out all the radios in the house. Neither Etienne nor Marie-Laure mentions the giant radio in the attic.

Sergeant Major von Rumpel arrives at the Natural History Museum in Paris. He threatens the assistant director of the museum and the mineralogist until they show him where the Sea of Flames is kept, inside an ingenious box. The lump in his groin bothers him.

Citizens who violate the blackout restrictions are interrogated, while the hotel where the Nazis stay is lighted all night long. Etienne and Marie-Laure move a giant wardrobe across the entrance to the attic to hide it.

Boys begin to leave the school. First, the boy who was chosen as the weakest member of the group, and then two others. Werner works in the professor’s laboratory on the design of a directional radio transceiver, refining the formulas for locating unknown points. He rarely hears from Jutta. He is learning to shut off his feelings, though he worries about Frederick, who seems to live in a world of his own. He protects Frederick by helping him with his chores. Frederick hates the older boys who kill birds for target practice.

Daniel receives a telegram on December 10, 1940, telling him to return to Paris at the end of the month. He is ordered to travel “securely.”

Daniel’s model of Saint-Malo is complete, containing the walled ramparts of the ancient city and all 865 buildings. Daniel spends the last night before his departure taking care of Marie-Laure. They have never been apart; he is to leave for Paris in the morning, and he tells her he will return within 10 days.

Frederick is identified as the weakest boy. He does not win the footrace to the safety of the commandant’s side. He is beaten unmercifully with the commandant’s rubber hose by the boy who identified him as the weakest. After this beating, when Frederick is asked if he is the weakest boy, Frederick answers no. Werner wants to help Frederick, but he merely looks on, only helping Frederick stand up once the beating is over.

Daniel LeBlanc is arrested by the police on his way to Paris. He is imprisoned and questioned about his keys and his tools; the Germans seem to be accusing him of plotting to blow up the Chateau de Saint-Malo. No one from the museum arrives to explain or to help him. He is driven away with other prisoners in the back of a truck headed toward Germany.