The traitor's emblem : a novel / Juan Gómez-Jurado ; translated by Daniel Hahn.

Enhanced descriptions from Syndetics:

Based on a true story: A Spanish sea captain rescues four German castaways during a treacherous storm in 1940. He doesn't know who they are or where they came from, but one of them gives him a mysterious gold-and-diamond emblem before disembarking. Decades later, the captain's son receives a substantial offer for it and is told an astounding story behind the object: it holds the key to Paul Reiner's lifelong quest. . . .

Munich, 1919. After his family falls into disgrace, fifteen-year-old Paul dreams of the heroic father he never knew. But one night, seconds before committing suicide, Paul's cousin reveals a terrible secret about his father's death. This discovery turns Paul's world upside down and leads him on a hunt in Nazi Germany to uncover the mystery surrounding his father's death.

The Traitor's Emblem is an epic novel spanning decades of family betrayal, impossible love, and the high price of vengeance. Set against the menacing streets of Depression-era Munich and the cruel rise of Nazism, Gómez-Jurado's spellbinding thriller proves again that he is a master of narration.