In a branch of the Spreewald Biosphere Reserve, Daniel Bartko's body is discovered in an empty barge, caught in a sledgehammer. It is quickly assumed that Polish fur hunters were at work here. Detective Inspector Thorsten Krüger begins the investigation and learns that the nutrias, fur-bearing animals from South America, were introduced and bred in the Spreewald region during the GDR era because of their sought-after fur