It's Carnival time, and the Black Forest and Baar are in a state of emergency. The Villingen construction contractor Heinrich Berger is found dead the morning after the guild ball - right at the Schwenninger Narrenbrunnen and still dressed in his Narrohäs. Mysterious messages suggest that the murder may be connected to the "fifth season," and some clues lead to other Carnival strongholds. Teacher Hubertus Hummel and local journalist Klaus Riesle are hot on the murderer's trail, diving deep into the Swabian-Alemannic Carnival. It's pure stress for Hummel, especially since his daughter Martina is heavily pregnant.