All The Light We Cannot See by Anthony Doerr is a novel which explores the possibilities for good and the similarities between people so apparently different from each other, with very distinctive goals in life. Marie-Laure, who has gone blind, has a devoted father who does everything he can to improve her situation and her senses to ensure that she is not compromised by her blindness. He is a museum curator and the legendary diamond, almost perfect and with "red flames" at the center, is allegedly housed in his museum. This diamond, however, is presumed to bring misfortune to whoever keeps it, but it also ensures everlasting life, such as was granted to the prince from Borneo centuries before.
Marie-Laure has no idea that, when she and her father were forced to flee from France and from Nazi occupation, her father brought the diamond (or an exact copy of it) with him and has hidden it in her uncle's house where they are staying. Unfortunately, her father is arrested by the Nazis and Marie-Laure is left with her eccentric uncle and his housekeeper, all of whom join the Resistance.
In the meantime, a young German boy, Werner, and his sister, Jutta, orphaned by the war, must occupy their time and Werner finds he has a talent for math and can manipulate the old radio he finds. He even listens to radio shows he overhears on the radio. His technical talent will ultimately gain him a place in an academy where, after he leaves, his skills will be used for what he discovers are not noble reasons. Werner's ability to interpret radio signals helps the Nazis track illegal messages and Werner feels responsible for the "child...with a bullet in her head," when innocent people, perpetrators in the eyes of the Nazis, are discovered. Werner, despite his exposure to the Hitler Youth, is not an advocate of the Nazis and the human cost is too much for Werner who negotiates his way through the devastation where his life will coincide with Marie-Laure's when he intercepts her secret radio transmissions. Instead of reporting her, as she relates Jules Verne's Twenty Thousand Leagues Under the Sea, he goes to help her.
By coincidence and through his efforts to locate the diamond, Seargent Major Reinhold von Rumpel, a Nazi officer, will attempt to scupper everyone's chances as he searches for the legendary gem. Marie-Laure, who wondered as a young girl why, in keeping with the legend, and in view of all the misfortune which befell everyone who owned it, the diamond was not returned to the sea, must make the decision of what to do with the one in her own possession. Leaving it in the grotto seems like the best thing to do, especially as so much harm and destruction have resulted from the search for it. The bottom of the ocean is definitely the best place for it, and the reader is left wondering whether Werner takes it from the grotto and throws it in the sea, ultimately breaking the curse but suffering his own death (from a land-mine) because of this or whether his death is coincidental.