Set primarily during World War II, "All the Light We Cannot See" traces the stories of two main characters whose lives eventually intersect: Marie-Laure LeBlanc, a blind French girl living in Paris with her father, and Werner Pfennig, a German orphan in a coal-mining town. Marie-Laure and her father flee to the walled city of Saint-Malo to escape the German occupation, carrying with them a priceless jewel. Meanwhile, Werner is recruited by the Nazi regime because of his skill with radios. The story explores the destructive nature of war, ethical themes, and a fascination with science and nature, leading up to the Battle of Saint-Malo in August 1944.