Crime writer Erica Falck is shocked to discover an old Nazi medal among her late mother's belongings. Inspired to to dig deep into her family's past, she visits a retired history teacher for answers. Two days later he's dead. Detective Patrik Hedstrom is on paternity leave. But his wife's inquiries appear to have set off a chain of murders and he's finding it hard to keep out of the investigation. A terrible secret from the darkest days of World War II is coming to light - and their families' histories are right at the heart of it.