It was just an ordinary Sunday afternoon in Dimpfelmoser's life: a hearty bratwurst meal was on the agenda. But then Dimpfelmoser's grandparents reveal to him that they are moving to a retirement home on the Wörther Schlossberg and want to transfer their house to him. The only condition: Dimpfelmoser must finally get married. Just at that moment, his colleague Reindl calls - a dead body has been found in the Danube. The deceased is a particularly prominent resident of the retirement home: Toni Hengersberger, honorary chairman of almost all local associations. Dimpfelmoser has to investigate in his usual rough manner - the fact that his grandparents want to join in as undercover investigators does not sit well with him at all...