It's the last night of 1899. In Helsingfors they celebrate the new millennium. The students at the university are dancing and among them is Helge Ulfstjerna.
Katja is about to graduate, but she has nothing to wear for the graduation ball. Her father, the eccentric inventor Carl Axel Kock does not spend much of his income on Katja while her brother Curry gets everything he wants. So on the day of the ball, Katja simply dresses up in her brother’s brand new evening attire and attends the dance, smokes cigars, drinks brandy–and causes a scandal.
A travelling theater-company performs Offenbach's "The Beautiful Helene" when an officer in the audience notices the similarity in appearance between the leading actor Leonard Pettersson and the king Charles XV.With Pettersson dressed as the king and the other actors as the royal suite, they all go to Herrsunda castle where the officer is trying to make an impression on his fiance.