March, 1902. When Herr Karl, head waiter of the Café Burg, is found dead at the foot of the Maria Theresa monument, it is assumed he slipped on the ice and hit his head. However, a witness has come forward who says otherwise, and private enquiries agent Karl Werthen is hired to investigate.

At the same time, Werthen is commissioned to locate a missing letter from the emperor to his mistress. Franz Josef is desperate for the letter not to fall into the wrong hands – but what incendiary information does it contain?

As Werthen and his colleague, renowned criminologist Dr Hanns Gross, pursue their investigations, it becomes increasingly clear that there is a connection between the two cases – and that the future of the empire may be at stake.