Chief Inspector Struhlmann, known as Struller, senses something terrible. In the cellar of the traditional Uerige brewery in Düsseldorf's old town, the longest-serving Köbes is found dead, killed by a falling barrel of altbier. An accident? The back of a male corpse in a monk's robe, discovered in an underground stone cave near Lohausen, is covered with oddly arranged small stab wounds. Struller recognizes an unfamiliar symbol in this. Not an accident! When a third body is found with a glassy stare fixed on the flowing Rhine, Struller needs support. He recruits his old intern Jensen, who is stationed at a small police station in the countryside near the Dutch border and, according to Struller, isn't learning anything useful there anyway. Their investigations take the mismatched team across both old and new Düsseldorf.