A dead woman is found in a stable in Aachen, an editor's cat is kidnapped and a publisher is put under pressure. The clues lead Inspector Fett to Simmerath, Zülpich, RWTH Aachen University and Liège. There, his colleague Kalumba needs his help because someone is blackmailing the city with an attack on the celebrations for Georges Simenon's 120th birthday. Are all the cases connected? The hunt for the unscrupulous perpetrator leads the detectives to Lake Rursee. When a shipwreck threatens, Fett resorts to the last resort.