Ostfriesenblut

An unknown person leaves a corpse on the doorstep of chief inspector Ann Kathrin Klaasen. The old woman does not remain the only victim. The murderer draws the chief inspector deeper and deeper into his perfidious game, the rules of which she does not know. Ann Kathrin Klaasen and her colleagues are working feverishly. What is the connection between the victims? Why did they have to die, and why are all the victims of retirement age?