Schwerin is sweating. It's the hottest summer in years. Detectives Lona Mendt and Frank Elling investigate a man who was hung upside down in his bathroom with his throat cut. When another victim is murdered shortly thereafter, the act of a serial killer becomes apparent.

Frank Elling and Lona Mendt have to cross moral and legal boundaries to get to the motive for the murder series and thus the masterminds behind the conspiracy.