The executioner's daughter and her father's legacy

The old executioner Jakob Kuisl is now plagued by all manner of ailments and worries. A letter from his old friend Nepomuk pulls him out of his gloomy mood. He invites Jakob to Passau and asks him to help in the search for a legendary treasure. The executioner doesn't hesitate for long and sets off on his journey. However, upon arriving in Passau, he discovers that Nepomuk is dead. And that four other veterans have arrived in response to their former companion's call. The former mercenaries swear they will catch their friend's killer. At this time, Vienna is under siege by the Ottoman army and the clouds of war are gathering over Europe. Will the Imperials defend it, or will the Turks invade this metropolis on the Danube?