At Gabriel Eisenstein’s home, Alfred gives a serenade to his ex-girlfriend, Rosalinde, Eisenstein’s wife. Adele, the maid of the house, has received an invitation from her sister Ida to go to the party at Prince Orlofsky’s villa that night. In order to obtain a free day, she lies to her mistress saying she has a very ill aunt and asks a leave to pay her a visit, but Rosalinde cannot do without her just the very same night her husband must start a five days arrest for insulting a police officer. Eisenstein arrives outraged: thanks to his lawyer now is eight days instead of five. Falke, Eisenstein’s best friend, arrives to invite him to a banquet at Orlofsky’s palace. Eisenstein decides to accept and show up the next morning to jail. To avoid being recognized, he will introduce himself as Marquee Renard, a foreigner. Rosalinde decides to grant permission to Adele to visit her aunt, anxious about meeting Alfred. Eisenstein leaves “on his way to prison” as Adele leaves “to visit her aunt”. That is how Rosalinde is left alone, to welcome her ex-boyfriend Alfred. Soon he arrives, seductive, but soon enough also does Frank, the Prison Director, looking for Eisenstein. It becomes impossible for Rosalinde to explain what another man is doing in her house alone, so Frank takes Alfred in her husband’s place. In Prince Orlofsky’s party, Ida is surprised to see her sister, because she did not send an invitation. Anyhow, she decides to introduce her as an up-and-coming artist: Olga. Orlofsky is bored, as is his usual, but Falke promises some fun with a farce entitled “The Revenge of the Bat”. Eisenstein arrives, in raptures with the idea of a party, alcohol and young girls, but he recognizes Adele. However, she insists on keeping the façade and insist on him calling her Olga. The Chevalier Chagrin also arrives to the party, but he is no other than Frank, the Prison Director, also going by as a French gentleman. Finally arrives Rosalinde, also a Falke guest, posing as a Hungarian Countess. Some time ago, in a costumes party, Eisenstein left Falke by himself sleeping drunk below a tree disguised as a Bat and had to look for his way home in daylight, for the amusement of the people who saw him. Since then he is known as Doctor Bat, and is looking for revenge on Einsenstein. He tries to conquer the Hungarian Countess. Rosalinde plays along until she captures her husband’s pocket watch, as evidence. In jail, Frosh, the Prison Officer, lets Frank know that M. Eisenstein has asked for a lawyer, and he has called a certain Dr. Blind. Ida and Adele (as Olga) arrive at the prison looking for Chevalier Chagrin. Adele confess she is not an actress, but she asks for help to break into the theatre world. Eisenstein arrives and he and Frank both confess their identities, but Frank is sure they have already under custody an Eisenstein since the night before. When Dr. Blind arrives, Eisenstein wears the lawyer’s wig and cloth to take his place and interrogate Alfred and Rosalinde. Both declare the idea was to teach a lesson to Eisenstein and he, furious, reveals his identity. But Rosalinde shows him the pocket watch she took from Eisenstein, and he still must stay in prison for another seven days, since there’s still most of his sentence to be done. Eisenstein is confuse as to how things have develop, until Falke explains to him that everything was part of his revenge. Eisenstein asks for Rosalinde’s forgiveness, since everything has been the champagne’s fault… and Rosaline gives up.