From the street outside the Eisenstein residence, drifts the voice of Alfred as he serenades his old flame, Rosalinda, Eisenstein’s wife. The maid, Adele, who has received an invitation to a masked ball, asks Rosalinda for an evening off, pretending that she is needed by an ailing aunt. Rosalinda, who has heard Alfred’s serenade, is much too preoccupied to pay attention to Adele. Eisenstein and his

lawyer, Dr. Blind, now come in from a session at court during which Eisenstein has received a jail sentence for having struck a policeman. Dr. Falke turns up with a suggestion that Eisenstein postpone his imprisonment for a few hours in order to attend Prince Orlovsky’s ball, unknown to his wife. Rosalinda and Adele bid farewell to Eisenstein who goes off to jail in full dress. He is hardly out of the house when Alfred returns with his protestations of undying love. The tête-a- tête is interrupted by the jail warden, Frank, who mistakes Alfred for Eisenstein. Rosalinda persuades Alfred to take her husband’s place and he is led off to jail.

The party at Prince Orlovsky’s is m full swing. The Prince welcomes his guests and exhorts them to drink and enjoy themselves. Adele, dressed in one of Rosalinda’s gowns, is recognized by Eisenstein who has arrived with Dr. Falke, and who is introduced as the Marquis Renard. Frank, the prison warden, also arrives as a guest. Eisenstein does not recognize his own wife when she enters disguised as a Hungarian countess. She excites his curiosity and he tries to flirt with her but only succeeds in losing his watch. As the entertainment and the drinking progress, Eisenstein suddenly realizes that it is time to leave for prison and the act ends as he and Frank help each other through the door.

Frosch, the jailer, is amusing himself by drinking. Frank, quite inebriated himself, arrives from the party and tries to get some sleep but is awakened by Frosch who insists on giving his daily report. Adele, looking for financial support from Frank whom she had met at the party, arrives to demonstrate to him her skill as an actress. Eisenstein arrives to begin his prison sentence and is amused to discover that Frank is the prison warden. Rosalinda hurries to the jail to rescue Alfred and is fooled when Eisenstein disguises himself as a lawyer. Although Eisenstein is enraged when he learns that Alfred has flirted with his wife, she counters by displaying the watch which she had taken from him at the ball. Falke explains that he engineered the entire situation as “The Revenge of the Bat” and all hurt feelings are restored.