The enterprising Anton Klapproth runs a flying duck farm in the Eifel, but now he finally wants to experience a real adventure in the big city of Cologne. A visit to a sanatorium for the mentally ill seems particularly sensational to him, as there is certainly a lot going on there with the "Jecken" and would provide plenty of story material for his regulars' table. In return for a loan, Anton's nephew allows his uncle to stay at the Pension Schöller. However, the guests there are by no means mentally ill, just rather eccentric. However, the unsuspecting Anton has a great time, thinking he is in a psychiatric institution.

The world was turned upside down on November 9, 1989. Not only does the Berlin Wall fall, but the German-German border in the Werra Valley is also rolled down...

It was Peter's idea to invite his friends on a joyride on Justus' birthday of all days. In pouring rain, a car breakdown forces the three detectives to seek refuge at the creepy "Blackstone" castle. When lightning knocks out the power line, the three investigators are stuck for good. It soon becomes clear to the three junior detectives that the lord of the castle, Count Gallagher, is a real chess fanatic. But not only that - the old castle makes a spooky impression and then there is Moe, the count's sinister servant. What is it about the chess pieces on the dilapidated, centuries-old chess table that seem to move by themselves, move after move, as if by magic? Is the old building really haunted? The first detective is immediately hooked and senses a new case, only Peter wants to run away. It soon becomes clear to the three investigators that this is about much more than just a game of chess...