Season 4

A man collapses in Beethovenstrasse. His murderer flees. The dead man, a private detective from New York, was on the trail of an international blackmail ring. Supported by customs investigator Kressin, Sandy, the dead man's partner, takes over the case. He manages to sneak into the blackmail ring. But the turbulence of the Cologne carnival makes the case more and more confusing, inscrutable and ultimately ends in a dark, bloody nightmare.

Having just arrived by plane from Istanbul, Kressin is waiting at the baggage carousel, keeping an eye on the charming Asian woman Lyn, who was sitting next to him on the plane. Instead of his suitcase, a corpse is wheeled up, and Lyn has suddenly disappeared. Since 350,000 marks were found on the dead man, Kressin searches for the murderer in the smuggling world and stumbles upon two chess pieces that cause a stir.