A Rough Guide

We are in Speisesaal with Ernest Dummkopf's acting company rehearsing.  But all this is a front for a plot to overthrow Rudolph, the Grand Duke.

Despite secret signs, Ludwig, the company comedian betrays the plot.

Meanwhile, blissfully unaware the Duke is planning his wedding to Baroness von Krakenfeldt.  But, as ever, it appears that the Duke was previous betrothed to the Princess of Monte Carlo, a problem!

After much confusion Ludwig assumes the role of the Grand Duke.  Upon the arrival of the Prince and Princess of Monte Carlo.  More weddings are arranged.  But, Ernest and Rudolph appear and denounce Ludwig as an impostor.  A legal oversight is reveals and "normality" is restored.