When marine archaeologist Dr. Emma Sinclair inherits her estranged grandfather's lighthouse on the remote Maine coast, she expects to find nothing more than a crumbling tower and painful family memories. Instead, she discovers a hidden room containing decades of coded journals, vintage photographs, and maritime logs that reveal an explosive secret: her grandfather Thomas was part of a clandestine network of lighthouse keepers who guided Jewish refugees to safety during World War II.

But as Emma deciphers the records, she uncovers a devastating betrayal. Klaus Weber, a trusted ally who provided submarine intelligence to the network, was actually a Nazi spy. His final act of treachery led to the sinking of the Étoile de Mer—a refugee ship carrying 47 souls and millions of dollars worth of artwork stolen from Jewish families.

Armed with coordinates her grandfather preserved for eighty years, Emma embarks on a dangerous quest to locate the lost ship. But she's not alone in her search. International treasure hunters, government agencies, and descendants of both heroes and villains converge on the discovery, each with their own agenda for the cultural treasures lying beneath the Atlantic waves.