IN a fashionable watering-place, described as near a big city, lives Gabriel von Eisenstein, a wealthy man of independent means, with his attractive wife Rosalinda, and their maid Adele. The light-hearted story of Die Fledermaus tells of the revenge taken by a certain Dr. Falke on this Gabriel von Eisenstein for playing a practical joke on him. When the story opens von Eisenstein is in trouble with the law and has been sentenced to prison for eight days for using abusive language to a policeman. Despite all the efforts of Blind, his advocate, to get him off, von Eisenstein is due to start his sentence by midnight and is spending the day preparing for prison, while his wife, Rosalinda, packs all his oldest clothes to wear in gaol. While she is away Dr. Falke, a notary and von Eisenstein's closest friend, arrives. He bears an invitation for von Eisenstein to a party to be given that night by Prince Orlofsky. "All the ladies from the ballet will be there," he tells von Eisenstein, and he suggests that he should postpone his surrender to the prison authorities till the following day and enjoy a last night of glorious revelry, wine, women and song. Von Eisenstein eagerly accepts Prince Orlofsky's invitation, little suspecting that it is the first move in Dr. Falke's plan of revenge. Adele, the maid, has a sister among the dancers who are invited, and she herself receives a letter suggesting that she borrow one of her mistress's evening dresses and impersonate a dancer for the occasion. After some difficulty she obtains permission to have the evening off. Von Eisenstein then bids Rosalinda a tearful farewell and departs, ostensibly to prison, in full evening dress, much to her amazement. Johann Strauss' music to this farewell scene is a masterpiece of comic irony.

No sooner are Rosalinda's husband and maid out of the house than the inevitable lover appears. In this case it is Alfred, a bumptious tenor. Rosalinda entertains him to a cozy supper with champagne and they toast each other. But an embarrassing situation arises. Rosalinda and Alfred are supping tjte-`-tjte when the Governor of the prison, Herr Frank, arrives on the scene. He has come to arrest von Eisenstein in person. Alfred attempts to deny that he is the man, but Rosalinda assures the Governor that that is only Herr von Eisenstein's fun. Careful of her reputation, she presses home the point. She is von Eisenstein's wife, that is her husband's dressing-gown: how can its occupant not be her husband? There is no escape for Alfred, and his only consolation is a series of farewell kisses before being led away to prison.

At Prince Orlofsky's ball the fun is fast and furious. As the "Marquis Renard" von Eisenstein has been presented by Dr. Falke to a young woman in whom he detects a likeness to his wife's maid, Adele; who indeed is she. In a charming little song she asks the Marquis what lady's maid ever had a hand or foot like hers, to say nothing of her Grecian profile, her figure and her frock (which is, of course, Rosalinda's).

Later in the evening Prince Orlofsky introduces the guest of honour, a Hungarian Countess wearing a mask. Von Eisenstein is greatly attracted by the Countess, little suspecting that the mask conceals the features of his own wife. Rosalinda's appearance at the party has been stage-managed by Dr. Falke as the final move in his revenge. Von Eisenstein flirts outrageously with the Countess and, as a result of his advances, she sinks down on a sofa, pressing her hand to her heart. She pretends that her heart has always been her weakness and she aks von Eisenstein to take her pulse. During the operation she manages to annexe his repeater watch, and thus holds a valuable piece of evidence of her husband's misdemeanours. This enchanting tik-tak duet is one of the highlights of Johann Strauss' score.

At supper the conversation turns on the practical joke that was played on Dr. Falke by von Eisenstein, who, forgetting that he is temporarily masquerading as Marquis Renard, regales Prince Orlofsky and his guests with the story. It appears that in their youth von Eisenstein and Dr. Falke both attended a fancy-dress ball in a country house two miles from town. Von Eisenstein went as a butterfly and Dr. Falke as a bat (Fledermaus), tightly sewn up in a brown skin, with long claws, broad wings and a yellow beak. When morning came Dr. Falke had drunk more than was good for him, and on the way home through the woods von Eisenstein, assisted by the coachman, lifted him out of the carriage and placed him under a tree and left him sleeping, unconscious of his fate. When he woke, the poor man had to walk home, still in fancy dress, through the town in broad daylight, to the joy of all the street arabs, and after that he was always known in the district as "Dr. Bat". This story is greatly enjoyed, particularly by a certain M. le Chevalier Chagrin, whose adopted name conceals the identity of Herr Frank, Governor of the prison. Without either of them having any idea of their respective identities, he and von Eisenstein strike up the warmest friendship. By now the champagne has had effect and everyone is feeling mellow. All join in a chorus in praise of champagne, the king of wines, and, at Falke's suggestion the whole company, glass in hand, swear eternal brotherhood and sisterhood. Finally, as 6 a.m. strikes, von Eisenstein and Herr Frank both hurry off on their independent ways to prison.

Act Three takes place in the prison, and here misunderstandings are cleared up. Rosalinda's possession of von Eisenstein's watch is compensated for by the presence in prison of Rosalinda's lover, Alfred, arrested while masquerading as her husband. As von Eisenstein philosophically declares, it's best to blame it all on the champagne.