A half-mutilated torso is found in the river Spree, meanwhile tango music drifts over from Monbijou Park where people are dancing outside. The two faces of Berlin are now in stark contrast. Warren Fischer and Judith Hellwig wonder if the third corpse is the work of a serial killer and they fear for a fourth victim. The motive is still unclear, but one thing is certain: the victims are men. The only common factor is that they were found in the same quadrant of Berlin.During their investigation, it becomes certain that the killer is honing the art of torture and one member of the team is pushed past their limit. The motive becomes clear as the team investigates past relationships. A silent witness provides the last piece of evidence, which confirms the killer, but time is running out. The question remains, what triggered the person to start the slaughter?