The Vienna Opera in his time - feudal and murderous! Allow me to introduce Gustav von Karoly, private detective and bon vivant in turn-of-the-century Vienna, passionate liberal, half-noble, and a great friend of women. With his beloved Dorothea staying far away in Zurich, distraction is on the agenda. What could be better than the feudal court opera? They are performing Otello. But when he receives the inevitable dagger stab, he collapses to the ground - the blood is real. The dagger is too. The crackling eroticism of Vienna's variety shows meets the chic of the Fin de Siècle. The charming private detective witnesses the drama and dives headfirst into the investigation. What lies behind the bloody deed: jealousy, revenge, competition? It quickly becomes clear - many in the esteemed ensemble are suspicious. Yet, just like the police, Gustav makes little progress in the case.