All the Light We Cannot See covers five primary periods in the lives of Marie-Laure LeBlanc and Werner Pfennig:

1. Childhood Before the War

Marie-Laure lives in Paris with her father, a locksmith for the Museum of Natural History. She goes blind because of cataracts, and he helps her cope with blindness by buying her Jules Verne adventure novels written in Braille and by building her a wooden replica of their neighborhood so she can learn to navigate it blind. As rumors of German occupation grow, the museum entrusts Marie-Laure’s father with a valuable diamond named the Sea of Flames. He and Marie-Laure evacuate Paris to deliver the stone to a friend of the museum.

Werner grows up in the countryside of Zollverein, Germany, together with his sister, Jutta, in an orphanage run by Frau Elena. Werner is inquisitive and gifted with science and mechanics. He discovers a broken radio and fixes it; he and Jutta use the radio to listen to a French professor deliver broadcasts about science. Though Werner dreams of becoming a scientist, he is told that he will be sent to work in a coal mine when he turns 15. His chance to escape this fate comes when he repairs a Nazi official’s radio and is offered a place at a Nazi school in Schulpforta.

2. New Homes and the Onset of War

The man to whom Marie-Laure’s father is supposed to deliver the Sea of Flames has fled to London, so Marie-Laure and her father continue to her great-uncle Etienne’s house in Saint-Malo and begin living there. Her father builds her a model of Saint-Malo and hides the Sea of Flames inside the replica of Etienne’s house. The Germans confiscate all the radios in Saint-Malo, but Etienne keeps one hidden in his attic. Marie-Laure’s father is summoned to return to the museum, but on his way he is arrested and sent to a prison camp in Germany.

The environment at Schulpforta is brutal for Werner, whose only friend is Frederick, a gentle boy who loves birds. Frederick is singled out for punishment, especially after he refuses to participate in killing an enemy prisoner. He is beaten so badly that he nearly dies and is sent home, his mind permanently damaged. Meanwhile, Werner’s technical genius is recognized by the science teacher, Dr. Hauptmann, who trains Werner to calculate the location of radio broadcasts using trigonometry.

3. Joining the War Effort

Etienne’s housekeeper, Madame Manec, organizes a group of women to fight for the French resistance against Nazi occupation. She tries to recruit Etienne to use his radio in the resistance movement, but he refuses because of the danger. Madame Manec dies of pneumonia, and after mourning her loss, Etienne and Marie-Laure decide to take up her resistance efforts. Marie-Laure receives loaves of bread from Madame Ruelle that have slips of paper with Allied intelligence baked inside. Etienne broadcasts the information on these slips using his radio. When Madame Ruelle learns the Allies are coming on D-Day, she asks Etienne to chart the locations of Nazi anti-aircraft guns and broadcast them. He tries but gets arrested.

As the German war effort becomes more desperate, Dr. Hauptmann lies and claims that Werner is 18 instead of 16 so Werner can be sent into the military. Werner joins a special team that hunts down anti-German radio broadcasts and kills the broadcasters. His team is called to Saint-Malo to locate the origin of one such illegal broadcast, which Werner recognizes as reminiscent of the French professor’s broadcast he listened to in his youth. Instead of telling his team about the broadcast, Werner locates it himself, finds Marie-Laure, and falls in love with her.

4. The Bombing of Saint-Malo

This piece of the story, which is broken up into narrative sections that fit chronologically with the novel’s plot progression, depicts the characters alone with their thoughts. The Allies begin bombing Saint-Malo. Werner takes shelter in the basement of a hotel; bombs cause the hotel to collapse, trapping Werner and Volkheimer, Werner’s team leader. Marie-Laure hides in Etienne’s cellar until the bombing is over. She climbs to the third floor for water and hears German officer von Rumpel, who desperately wants to locate the Sea of Flames, enter the house looking for the diamond. She hides in the attic, which has a secret entrance von Rumpel cannot find.

After days in the attic, Marie-Laure begins broadcasting. Werner has managed to fix his radio, and he and Volkheimer hear her reading. At one point she pauses and whispers, “He is here,” alerting Werner to the fact that she is in danger. Tired of waiting to be discovered, Marie-Laure begins playing loud music. Volkheimer hears the music through the radio, and it inspires him to risk his life blasting a way out of the hotel basement rubble where he and Werner are trapped. Werner goes to Etienne’s house and rescues Marie-Laure by killing von Rumpel. He helps her escape the city after putting the Sea of Flames and the model of Etienne’s house in an ocean grotto. Werner and Marie-Laure part ways. Marie-Laure reunites with Etienne while Werner is taken prisoner by the Allies and grows ill. He deliriously wanders into a minefield, triggers an explosion, and is killed.

5. After the War

Jutta is in Berlin when Russian soldiers arrive, and three of them rape her. Marie-Laure and Etienne move to Paris, where Marie-Laure begins school.

Decades later, an organization gives Werner’s belongings to Volkheimer, who brings them to Jutta. Among them is the model of Etienne’s house. Jutta goes to Saint-Malo to learn about her brother’s last days alive, and she recognizes that Etienne’s house matches the model. A neighbor puts her in touch with Marie-Laure, who now works at the Museum of Natural History. Jutta meets Marie-Laure, tells her that Werner died, and gives her the model house. Marie-Laure realizes that Werner must have retrieved it from the grotto after they parted ways. When she opens it, she finds the key to the grotto gate. She wonders what he did with the Sea of Flames; although she has no way of knowing it, the narrator reveals that Werner left the diamond in the grotto.

Many years later, Marie-Laure goes to a park with her grandson, where she reflects on her life and loss.