In Vienna, the rich Prince Orlofsky is deeply bored. To distract himself, he gives a masquerade: Dr. Falke; Gabriel von Eisenstein; his wife Rosaline, disguised as a Hungarian princess; Adèle, her maid… everyone is there, under a variety of pretexts. Eisenstein seduces all the women he meets, including his own, whom he does not recognize. Eisenstein, under legal trouble for having hit a policeman, returns to prison to serve his sentence. And lo and behold, the guests arrive one after the other… and the events are precipitated: Adele charms the prison warden, Rosaline confronts her husband and confesses that the evening is nothing more than a prank planned by Falke: it’s the revenge of the bat!