Karolin, Chris, and Philipp — the horse club and neighborhood detectives — take on a new case. Their friend Anne is competing in the casting for Arena Caballo, one of the world's most famous equestrian shows, and looks like the frontrunner. Then her horse Lajana shies unexpectedly during a performance and is seriously injured. Anne's chances of making the show are suddenly in doubt. The horse gang wants to know whether this was an accident or something deliberate.