How does All the Light We Cannot See end?
In the final act, as American forces bombard Saint-Malo in August 1944, Marie-Laure hides with the Sea of Flames diamond, first in the cellar and then in the attic of her great-uncle Etienne's house, evading the dying Nazi gemologist von Rumpel, who has torn the house apart searching for the stone. Unable to find it, she uses Etienne's hidden radio transmitter to broadcast readings from Twenty Thousand Leagues Under the Sea along with pleas for help, not knowing who might hear.
Across the city, Werner Pfennig, along with his commander Volkheimer and fellow soldier Bernd, is buried in a cellar after their hotel is bombed. Bernd dies of his wounds. Werner repairs a radio and picks up Marie-Laure's broadcast, recognizing it. After days trapped, Volkheimer has Werner detonate a grenade to blast them free. Werner makes his way to Etienne's house, finds the delirious von Rumpel, and shoots and kills him, saving Marie-Laure. The two share a brief, tender connection; Marie-Laure gives Werner the key to a seaside grotto where she has hidden the Sea of Flames, releasing it into the ocean as the legend demanded, and Werner sends her off to safety before he is captured by American forces.
Werner, weakened by an illness he never recovered from, is taken to a POW camp. Delirious one night, he wanders out of the hospital tent and steps on a German landmine, dying instantly. Etienne survives his imprisonment at Fort National and is reunited with Marie-Laure after the battle. Neither of them ever learns what happened to Marie-Laure's father, Daniel, who had been arrested years earlier and disappeared into German custody.
The novel closes with two epilogue movements. Thirty years later, Volkheimer receives Werner's few belongings, including the small wooden model house that once held the diamond, and delivers them to Werner's sister Jutta, now a married math teacher, telling her Werner may have been in love. Jutta and her son Max travel to Paris and meet Marie-Laure, now a marine biologist at the Museum of Natural History. Opening the model, Marie-Laure finds the key to the grotto and is left wondering whether the Sea of Flames remains at the bottom of the sea or whether Werner somehow took it with him. Finally, the story leaps to 2014, ending with Marie-Laure, now eighty-six, walking through the streets of Paris with her grandson Michel, the past folded quietly into the present.
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