Marie-Laure is a blind French girl living in Paris with her father, who works at the Museum of Natural History. Her father constructs a miniature replica of their neighbourhood so Marie-Laure can navigate the city on her own. When the Germans invade Paris, Marie-Laure and her father flee to the coastal town of Saint-Malo, taking with them a valuable and mysterious jewel from the museum.
Werner Pfennig is a German orphan with a natural talent for fixing radios. He is recruited by the Nazis and sent to a brutal military academy. Werner's intelligence and technical skills earn him a place in the German army, where he is involved in tracking down illegal radio transmissions. However, as Werner witnesses the horrors of war and becomes increasingly disillusioned, he begins to question the actions of the Nazi regime.
The lives of Marie-Laure and Werner eventually converge in Saint-Malo, where they face the devastating consequences of the war. Marie-Laure's father, who was involved in the French Resistance, is captured by a German officer named Von Rumpel, who is desperate to obtain the valuable jewel.
As the war reaches its climax, Marie-Laure and Werner's paths cross, and they find themselves caught up in a dangerous and desperate situation. The story explores themes of bravery, humanity, and the power of hope amidst the darkness of war.