The scene is set in Paris in the 1890′ s.

The story begins before the rise of the curtain. Fadinard, a bachelor about to marry Elena, the daughter of a country bumpkin, Nonancourt, has gone to Charantonnau to fetch his bride. On the return trip, when he alights to retrieve a fallen whip, his horse wanders into the woods, encounters a prettily trimmed straw bonnet hanging from a tree, and mistakes it for a meal. Its owner-a lady who has gone off for a stroll in the company of a soldier-suddenly appears, hysterical to find her hat half-eaten. When her companion threatens violence, Fadinard makes his escape.

Scene 1: The salon of Fadinard s house. The servant Felice ushers in the first of the wedding guests – the bride’s deaf old Uncle Venizet – who has arrived with an elaborately wrapped wedding present. An agitated Fadinard appears and recounts his misadventure in the woods. He is interrupted by the arrival of Anaide, “the hat lady,” and her soldier-friend, Emilio. They demand that Fadinard provide them with a straw hat to replace the one his horse has eaten. Dispatching Felice to the nearest milliner, Fadinard manages to hide the unwelcome visitors in an adjoining room just as his fiancée and future father-in-law appear. Nonancourt, eager to proceed with the wedding ceremony, threatens to call the marriage off. After a tender moment alone with Elena, Fadinard persuades her and her father to rejoin the wedding guests and promises to appear at the city hall at the appointed hour. As Felice returns-empty-handed-Anaide and Emilio emerge from hiding. They refuse to leave the house until another hat can be found.

Scene 2: A milliner’s shop. Trailed by the wedding party, Fadinard makes the rounds of all the hat-shops in the city. A sympathetic milliner tells him that she has just sold the hat he wants to the Baroness of Champigny. Fadinard leaves for the baroness’s villa in Passy.

Scene 3: A salon in Baroness de Champigny’ s house. The baroness is about to give a musicale featuring the celebrated Italian violinist Minardi, and, when Fadinard appears, she mistakes him for the virtuoso. Playing the part, and feigning a secret passion for his hostess, Fadinard begs her for some personal memento — her new straw hat. Flattered and confused, she is prepared to indulge the maestro’s eccentric whim, but the hat she offers is a black one. Fadinard noisily demands the other-the Italian-straw hat, and as the bewildered lady explains that she has sent it as a present to her relative, Mme. Beaupertuis, the real Minardi makes his entrance. Meanwhile, the bridal party, confusing the banquet for the long-awaited wedding supper, create an uproar among the assembled guests. As the police are summoned, Fadinard dashes off to the house of Mme. Beaupertuis.

A room in Beaupertuis’ s house. Beaupertuis, an ill-tempered old man, is waiting impatiently for his wife’s return: he is, in fact, Anaide’s “jealous husband”. Unaware of this, Fadinard bursts in melodramatically and demands the hat, and followed by the outraged Beaupertuis, storms off through the house to find it. The wedding guests appear, and thinking that the place is Fadinard’s, make themselves at home. Fadinard, in explaining why he needs the hat, unwittingly reveals to Beaupertuis Anaide’s indiscretion with Emilio. The husband, already beside himself, becomes apoplectic at the sight of his house overrun with strangers. After a moment of general confusion, Beaupertuis, brandishing a pistol, charges out to confront his faithless wife.

Scene 1: A street. As evening falls, the wedding guests trail through the city streets on the way to Fadinard’s, their spirits dampened by a sudden downpour.

Scene 2: A square in front of Fadinard s house. Fadinard rushes in, still hoping to save Anaide from her husband, but Nonancourt, thinking that his son-in-law has been keeping “another woman”, bellows that the marriage is null and void and demands the immediate return of the dowry. In the ensuing struggle old Uncle Venizet reveals that his gift to the young couple is-an Italian straw hat! While Fadinard dashes inside to tell the happy news to Anaide and Emilio, the police, suspicious at the steady flow of parcels from the house, arrest the entire wedding party for burglary. Beaupertuis storms in, and while Fadinard distracts him, Emilio succeeds in rescuing both the hat and the imprisoned guests. Nonancourt, now aware of the intrigue that has caused Fadinard’ s madcap behavior, salutes his son-in-law as a man of honor and puts his blessing on the marriage. Everyone goes home, leaving the bride and groom – blissfully reunited and alone at last – to do the same.