Act I

The storm clouds are gathering above the Viennese Herr Von Eisenstein's house. He has been sentenced to a five-day prison term for duelling. While he is away battling in court for acquittal, his wife Rosalinda is courted by and old suitor, Alfred, the famous tenor. Alfred tries to persuade his old flame to make good use of her brief grass widowhood. Rosalinda is about to be completely deserted: her chambermaid Adele tries to get the night off by telling her mistress that her ‘poor old aunt’ is deathly ill. In actual fact, Adele secretly wants to go to the ball at Prince Orlofsky's, to which she has been invited – so she is aware – by her sister Ida the ballerina. 

Eisenstein arrives home in deep distress. He is fighting with his lawyer, Dr Blind. His prison term has been extended to eight days because of Blind’s incompetence. Blind promises to appeal, but Eisenstein throws him out. He has only been allowed to come home for a farewell dinner. He sends Adele to the nearby restaurant to get him some comforting delicacies.

The lawyer Dr Falke comes to visit. He used to be the family’s friend until Eisenstein played a nasty trick on him. Three years ago the two of them had gone to a costume ball dressed as a butterfly and a bat. On the way home, Eisenstein got the doctor drunk and left him asleep in the park in his bat costume. Ever since everyone in Vienna has called him the Batty Doctor. However, this time – so it appears – Dr Falke has not come to gloat. He convinces Eisenstein to come to the ball at Prince Orlofsky's and postpone reporting to gaol (where he can recover from the spree) until midnight. He even asks Eisenstein to bring with him his famous chiming watch, used so effectively in his many conquests. Dr Falke secretly also invites Rosalinda to Orlofsky’s, and provides her with a costume. 

Adele returns the bountiful dinner, but her master hurries off with his crony, Dr Falke. Then, on the spur of the moment, Rosalinda decides to let Adele off for the night, and resigning herself to her fate she allows Alfred, serenading under her window, to enter, and continue at the dinner table. However, their intimate rendezvous is interrupted when Herr Frank, the director of the prison where Eisenstein is to spend his gaol term, enters. He has come to personally escort Eisenstein to his prison. Rosalinda begs Alfred to say that he is Eisenstein, to avert a scandal. Alfred agrees and leaves with Frank to take Eisenstein's place in prison.

Act II

Receiving his guests in his lavish palace, Prince Orlofsky is lamenting his terminal boredom and eventually ‘shoots himself in the head’ with a bottle of vodka. Dr Falke assures him that tonight he will laugh: he has planned a little comedy, whose unsuspecting actors enter the scene one after the other. 

Arriving in Rosalinda’s dress, Adele is introduced as an actress. Eisenstein is introduced as the Marquis de Renard, and is flabbergasted to see his chambermaid at the ball. Adele is equally horrified to see her master, but continues to insist that she is an actress. Eisenstein has a gruelling conversation in French with Chevalier Chagrin, who is in fact Frank. The ‘two illustrious’ Frenchmen woo Adele and Ida, while Falke introduces Eisenstein to the mysterious Hungarian countess, who is really Rosalinda. Eisenstein flirts with the woman, but loses his chiming watch in the process. He tries desperately to get it back, but his time is up, and he must begin his prison sentence.

Act III

Frosch, the gaoler, delivers an intoxicated soliloquy in the prison director’s office, when an equally inebriated Frank comes in. They have not even weighed up the tricky situation when Adele and Ida arrive. They take Frank (or Chevalier Chagrin, as they know him) by his word, and ask him to help Adele break into show business – she displays talent in a brilliant solo. 

Next, Eisenstein enters and is taken aback to find that his drinking mate, Chevalier Chagrin, is the director of the prison. His surprise is even greater when he learns that Herr Von Eisenstein was arrested the evening before, while he was at home, dining with his wife. 

Meanwhile, Alfred impatiently waits for the lawyer he has sent for. Rosalinda arrives, wanting to save the day. However, Eisenstein returns, disguised as the lawyer. Instead of help, he swears to take revenge on his unfaithful wife and her suitor. But Rosalinda counters his accusation by producing the watch she swindled out of him as a Hungarian countess. Eisenstein then changes tactic and denies his identity, but Adele identifies her master. 

Finally, Prince Orlofsky and all the party guests pour into the gaol. Dr Falke announces the whole situation was a joke – the revenge of the Bat. Eisenstein is reassured in his belief that Alfred too was just part of the joke. All is forgiven, everything is back to normal, only Adele becomes and actress, with the help of Orlofsky.

Act 1

Eisenstein's apartment

Gabriel von Eisenstein, a Viennese man-about-town, has been sentenced to eight days in prison for insulting an official, partially due to the incompetence of his attorney, Dr. Blind. Adele, Eisenstein's maid, receives a forged letter, allegedly from her sister who is in the company of the ballet, but actually written by Falke, inviting her to Prince Orlofsky's ball. She pretends the letter says that her aunt is very sick, and asks her mistress Rosalinde (Eisenstein's wife) for an evening off ("Da schreibt meine Schwester Ida"/"My sister Ida writes to me"). Falke, Eisenstein's friend, arrives to invite him to the ball (Duet: "Komm mit mir zum Souper"/"Come with me to the souper"). Together, they recall a practical joke which Eisenstein played on Falke a few years ago, for which Falke is secretly planning a light-hearted revenge in kind. Eisenstein bids farewell to Adele and his wife Rosalinde, pretending he is going to prison (Trio: "O Gott, wie rührt mich dies!"/"Oh dear, oh dear, how sorry I am") but really intending to postpone jail for one day and have fun at the ball.

After Eisenstein leaves, Rosalinde is visited by her former lover, the singing teacher Alfred, who serenades her ("Täubchen, das entflattert ist"/"Dove that has escaped"). Frank, the governor of the prison, arrives to take Eisenstein to jail, and finds Alfred instead. In order not to compromise Rosalinde, Alfred agrees to pretend to be Eisenstein and to accompany Frank. (Finale, drinking song: "Glücklich ist, wer vergisst"/"Happy is he who forgets" followed by Rosalinde's defence when Frank arrives: "Mit mir so spät im tête-à-tête"/"In tête-à-tête with me so late," and Frank's invitation: "Mein schönes, großes Vogelhaus"/"My beautiful, large bird-cage.")

Act 2

A summer house in the Villa Orlofsky

It transpires that Falke, with Prince Orlofsky's permission, is using the ball as a way of getting revenge on Eisenstein. Some time before, after a costume-party, Eisenstein had abandoned Falke, very drunk and dressed in a bat-costume, in the center of town, exposing him to ridicule the next day. As part of his scheme, Falke has invited Frank, Adele, and Rosalinde to come the ball, all concealing their identities as well. Rosalinde pretends to be a masked Hungarian countess, Eisenstein goes by the name "Marquis Renard," Frank is "Chevalier Chagrin," and Adele, who has borrowed one of Rosalinde's dresses without permission, pretends she is an actress.

The ball is in progress (Chorus: "Ein Souper heut' uns winkt"/"A souper is before us") and the Prince welcomes his guests ("Ich lade gern mir Gäste ein"/"I love to invite my friends"). Eisenstein is introduced to Adele, but is confused as to who she really is because of her striking resemblance to his maid. ("Mein Herr Marquis"/"My lord marquis," sometimes referred to as "Adele's Laughing Song"). Frank arrives. He and Eisenstein, who are both posing as Frenchmen, attempt to conceal their identities by repeating common French phrases to each other, to Orlofsky's great amusement. Since neither actually knows French, both are fooled. As the party progresses, they both experience alcohol-induced good-feeling and manly camaraderie for each other.

Then Falke introduces the masked Rosalinde to the company. She convinces everyone that she is Hungarian by singing the "Czardas", a sentimental dancing-song ("Klänge der Heimat"/"Sounds from home"). During an amorous tête-à-tête, Eisenstein tries unsuccessfully to persuade the mystery-woman to unmask. She succeeds in extracting a valuable watch from her husband's pocket, something which she can use in the future as evidence of his impropriety. (Watch duet: "Dieser Anstand, so manierlich"/"Her bearing, so well-mannered"). In a rousing finale, Orlofsky makes a toast to champagne, and the company celebrates (The Champagne song: "Im Feuerstrom der Reben"/"In the fire stream of the grape"; followed by the canon: "Brüderlein, Brüderlein und Schwesterlein"/"Brothers, brothers and sisters" and the waltz finale, "Ha, welch ein Fest, welche Nacht voll Freud'!"/"Ha, what joy, what a night of delight.") Eisenstein and Frank dash off as the clock strikes six in the morning.

(Note: The "Champagne song", which is sung by the entire ensemble, should not be confused with the baritone aria "Fin ch' han dal vino" from Don Giovanni, which is often called the "Champagne aria".)

Act 3

In the prison offices of Warden Frank

The next morning they all find themselves at the prison where the confusion increases and is compounded by the jailer, Frosch, who has profited by Warden Frank's absence to become gloriously drunk. Alfred, still in jail in Eisenstein's place, irritates the other prisoners by singing operatic arias.

Adele arrives to ask the Chevalier Chagrin (actually Frank) to sponsor her career as an actress, but Frank is not wealthy enough to do this (Melodrama; Couplet of Adele: "Spiel' ich die Unschuld vom Lande"/"If I play the innocent peasant maid"). Meanwhile, Alfred asks Frosch to summon Dr. Blind to help get him released; Frank agrees to allow this and Dr. Blind arrives. Eisenstein enters and says he has come to serve his sentence. He is surprised when Frank tells him that his cell is already occupied by a man who claims to be Eisenstein and whom Frank had arrested in Eisenstein's apartment. Frank further tells Eisenstein that the man he arrested was singing amorous songs to Rosalinde at the time of his arrest, and warmly kissed her goodbye. Enraged, Eisenstein takes Dr. Blind's wig and glasses in order to disguise himself and confront the impersonator Alfred, whom Eisenstein now believes has cuckolded him. Rosalinde enters. Eisenstein takes off his disguise and accuses her of being unfaithful to him with Alfred. Eisenstein, Rosalinde, and Alfred sing a trio in which Eisenstein angrily claims the right of vengeance (Trio: "Ja, ich bin's, den ihr betrogen...Ra-ra-ra-ra-Rache will ich!"/"I'm the one who was mistreated....Ve-ve-ve-ve-vengeance is mine!"). However, Rosalinde produces his watch, and he realizes that the Hungarian mystery-woman he tried to seduce at Orlofsky's party was actually Rosalinde in disguise and that he, not she, is at fault.

Falke enters with all the guests from the party and explains that the whole thing was payback for Eisenstein's practical joke on him three years before. Eisenstein is delighted by the prank, and he begs Rosalinde to forgive him for his attempted infidelity. Rosalinde refuses at first, and threatens to divorce him, but Eisenstein tells her that his misbehavior was caused by the champagne. She accepts this explanation and immediately forgives him unconditionally. Orlofsky promises to finance Adele's acting career, and the company joyfully reprises the "Champagne song" from Act 2.