Ten-year-old Leon, the foster son of an architect, is missing. Soon after, the boy is found murdered. Initial suspects are quickly identified, including Leon's biological mother, who has never fully escaped her dubious past. Her boyfriend also comes under suspicion, as does Leon's biological father. Then there's the somewhat questionable neighbor who spent an unusually large amount of time with Leon. And what about the foster mother? Katharina von Hagemann and her colleagues have many leads, but no concrete evidence. Will they still manage to find Leon's murderer, or will this be their first unsolved case?.