Karin and Paul are happily married without children. She is an ambitious homicide detective in Hamburg, who spends most of the time at the precinct and often takes her work home with her. He works as a school teacher and has no qualms having a lower profile career than his wife, whose work he takes an active interest in. Karin is close friends with fellow law enforcers Mike and his wife Dina, who are known for their banter, even now that they are getting a divorce.
When a Hamburg prostitute turns up murdered, the case proves itself to be a golden career opportunity for Karin, who finds herself hot on the heels of a serial killer.