[3][4] A mysterious circus performer known as "Mister X" captivates audiences with his breathtaking acts, including playing the violin while seated on a chair suspended in midair by ropes.

The enigmatic nature of Mister X intrigues Théodora Verdier, a young widow who has consistently rejected marriage proposals from a nobleman, the Baron.

Tony's mother accepts his relationship with Marie, and Théodora ultimately forgives Mister X, choosing love over societal expectations.

[5] Although the film was based on Emmerich Kálmán's Die Zirkusprinzessin, which had premiered at Theater an der Wien in Vienna on 26 March 1926, significant changes had to be made because the operetta was set in Tsarist Russia and as such had many themes which were unacceptable to the censors.

[8] The actor Grigory Yaron [ru] who played Pelican wrote: "No Kalman operetta made in the Soviet Union had as many different variants as The Circus Princess.