A room in the home of Gabriel von Eisenstein.
A tenor can be heard offstage, singing a serenade to the mistress of the house, Rosalinde. Adele, the maid, enters reading a letter from her sister, Ida, a ballerina, inviting her to accompany her to a ball arranged by the rich Russian prince, Orlofsky. In order to be able to go to such an event, she will have to “borrow” an evening gown from her mistress. The tenor, who continues his serenade, is a singer, Alfred, a onetime lover of Rosalinde’s before she married. Adele asks to have the evening off, saying that she must visit her sick aunt. Rosalinde immediately denies her permission: Adele will have to remain at home because on that very evening her mistress’ husband is to begin serving a short prison sentence for striking an officer. So the sobbing Adele cannot go with her sister and must stay with Rosalinde, who might otherwise be exposed to the temptation to yield to Alfred’s advances.
Eisenstein arrives arguing with his lawyer, Blind, over the extra three days that appeal court has added to the original sentence. Before he goes off to prison, he wishes to enjoy a delicious dinner and asks Adele to go and buy the food. However, Eisenstein is joined by his old friend, Dr. Falke, who persuades him to postpone going to prison and to go with him to Orlofsky’s reception instead. Eisenstein allows himself to be convinced, so long as his wife knows nothing about it. Rosalinde is amazed when she sees Gabriel ready to go to prison in full evening dress. But she doesn’t really care, now that she has the opportunity to meet her old admirer, Alfred, possibly with no witnesses. With this in mind, she gives Adele the evening off. Eisenstein and Adele pretend to be sorry that Rosalinde will remain alone at home and she too plays along with them in an amusing trio. Rosalinde can hardly express how she feels, when in comes Alfred acting as if he were the master of the house: he puts on Gabriel’s house jacket and begins to eat the delicacies that have been prepared. He then pours himself some wine and wants Rosalinde to join him. She begs him to leave, but without success. All of a sudden, the party is spoiled by the arrival of Frank, the new prison governor. He does not know Eisenstein and so takes Alfred to be the master of the house. Frank, like everyone else, is also bound for Orlofsky’s ball, but he informs them that first he has come to take Eisenstein to prison. To avoid compromising Rosalinde, Alfred agrees to go with him, and all the couple can do is kiss one another goodbye.
A salon and garden at prince Orlofsky’s villa.
The ball has begun at Villa Orlofsky and the guests are enjoying themselves while they await the prince’s arrival. Adele enters and comes across her sister, Ida, who is most surprised at seeing her there. Adele too is surprised: did Ida not send her a letter inviting her to the ball? Ida says that she has written no such letter and that it must have been a joke. She also expresses her embarrassment at finding such a low-ranking woman at the reception. Even so, she decides to make the best of an awkward situation and introduces Adele as an actress. Prince Orlofsky now arrives with Falke, and since the latter is bored to death, he asks him what might brighten up the party for him. The doctor already has a plan in mind: he wants to play a joke on Eisenstein in revenge for the time when his friend, after a carnival ball, had made him go home, in full daylight, wearing a bat costume. Ida introduces her sister to the prince as a new artiste called Olga. Falke whispers that she will be a character in his comedy. Eisenstein enters disguised as the marquess Renard. Falke asks the prince to keep him occupied while he tries to persuade the man’s wife, Rosalinde, to attend the ball. Orlofsky offers Eisenstein something to drink and he tells him that his only hope of being amused that evening lies in Falke’s promise to make him laugh at his, the marquess Renard’s expense. Eisenstein is a little taken aback, even more so since he believes he recognises Adele, his maid. Olga tries to convince him that he is wrong and that the resemblance is pure coincidence; in the end, Eisenstein believes her. Next arrives the chevalier Chagrin, who is actually Frank, the prison governor in disguise. A feeling of mutual liking develops between Chagrin and Renard. Some ladies would like to dine, but Falke tells them that they will have to await the arrival of a Hungarian countess, who wishes to remain anonymous and so will come wearing a mask. Everyone is very curious. Eisenstein continues to muse on the remarkable resemblance between Olga and Adele. He is fascinated by her and considers her much prettier than his maid, and so he decides to court her using his favourite system, that is, by swinging a valuable watch in front of the woman’s nose, leading her to believe that it could be a present.
Finally, Rosalinde makes her entrance dressed as a Hungarian countess. Falke has informed her that her husband is at the ball and not in prison. She soon spots her husband courting Adele, their maid, who also happens to be wearing one of her own dresses. Eisenstein-Renard and Frank-Chagrin approach Falke who introduces the countess to them. The woman’s husband, who has not recognised her, immediately decides to court her and shows her the usual watch, which she cunningly manages to filch from him in order to have undeniable proof of his unfaithfulness. The moment comes in which the guests are supposed to reveal their true identities. Rosalinde, however, is reluctant and, as proof of her Hungarian origins, she sings a czardas. Now the guests wish to hear the tale of the bat mentioned by Falke. Eisenstein recalls the joke he played on his friend a few years before and recounts it: after making sure that Falke had had a lot to drink, Eisenstein had left him, early in the morning, under a tree with his bat costume, leaving him no option but to cross the city dressed as a bat and laughed at by everyone. The guests like the story, but it is now time for dinner. Orlofsky sings the champagne aria and everyone celebrates to the sound of waltzes. Eisenstein again tries unsuccessfully to persuade the mysterious countess to remove her mask. At six o’clock in the morning, Eisenstein and Frank leave the villa rather the worse for wear, both headed for differing reasons to the prison.
The prison governor’s office.
It is dawn. Alfred, locked in a cell, is singing as at the beginning of the first act. Frosch, the drunken guard, tells him to shut up while he prepares the report for Frank, who is also still rather tipsy and suffering from the after-effects of the ball. The bell rings and Ida and Adele enter asking for the chevalier Chagrin. In Frank’s office, Adele confesses that she is not an actress, but that she would very much like to be one and she has therefore come to ask for Chagrin’s help. She performs for him, rousing his interest, and tells him she would like him to introduce her to a theatrical impresario. Frank does not even have the time to reflect on the matter, since the bell rings again and in comes Eisenstein-Renard ready to serve his sentence. Seeing the chevalier Chagrin, who informs him that he is the prison governor and that on the evening before he arrested Eisenstein, he is astonished – particularly when he discovers that the man arrested was dining with his wife, wearing his house jacket. The prison bell rings again announcing a veiled lady who wishes to speak to a prisoner. Frank goes to meet her and leaves Eisenstein somewhat perplexed. Finally, Blind enters, sent for by the prisoner who everyone believes to be Eisenstein. At this point, the real Eisenstein has an idea. He puts on Blind’s coat, wig and glasses and ensures that Rosalinde will be present. She has come to beg Alfred to flee in order to avoid compromising her by meeting her husband. Eisenstein-Blind subjects both her and Alfred to interrogation, demanding to know what happened at home on the previous night and above all, who the man under arrest in his place was. Then, furious, Eisenstein reveals his identity and accuses his wife, but Rosalinde indignantly shows him the watch that she has taken from him at the ball. It would appear that all the deceptions have come to a head, but Falke reveals that they have all been part of a comedy, the bat’s revenge. Somewhat confused, Eisenstein does not take it badly and the whole affair is solved: everyone blames the champagne, “the king of all wines”.