When the double murder in Linköping, Sweden, back in 2004 was finally solved after 16 years, it was a genealogist who made the breakthrough. For the first time in Europe, a murder could be solved through genealogical research.

During a snowy Christmas season in Sweden, psychologist and profiler Inger Johanne Vik and her autistic daughter both get drawn into the investigation of a number of disturbing deaths.