The "Daughter of the Regiment" happily combines Italian richness of melody with French "esprit" and French sallies, and hence the continued charm of this almost international music.
The libretto can be accounted good.
The scene in the first act is laid near Bologna in the year 1815, the second act in the castle of the Marchesa di Maggiorivoglio.
Mary, a vivandière, has been found and educated by a French sergeant, named Sulpice, and therefore belongs in a sense to his regiment, which is on a campaign in Italy. She is called the "daughter" of the regiment, which has adopted her, and she has grown up, a bright and merry girl, full of pluck and spirit, the pet and delight of the whole regiment.
Tonio, a young Swiss, who has fallen in love with Mary, is believed by the grenadiers to be a spy, and is about to be hanged. But Mary, knowing that he has only come to see her, tells them that he lately saved her life, when she was in danger of falling over a precipice. This changes everything and on his expressing a desire to become one of them, the grenadiers suffer the Swiss to enlist into their company. After the soldiers' departure he confesses his love to Mary, who returns it heartily. The soldiers agree to give their consent, when the Marchesa di Maggiorivoglio appears, and by a letter once affixed to the foundling Mary, addressed to a Marchesa of the same name and carefully kept by Sulpice, it is proved that Mary is the Marchesa's niece. Of course this noble lady refuses her consent to a marriage with the low-born Swiss and claims Mary from her guardian. With tears and laments Mary takes leave of her regiment and her lover, who at once decides to follow her. But he has enlisted as soldier and is forbidden to leave the ranks. Sulpice and his whole regiment curse the Marchesa, who thus carries away their joy.
In the second act Mary is in her aunt's castle. She has masters of every kind for her education in order to become a lady comme il faut, but she cannot forget her freedom, and her dear soldiers, and instead of singing solfeggios and cavatinas, she is caught warbling her "Rataplan", to the Marchesa's grief and sorrow. Nor can she cease to think of Tonio, and only after a great struggle has she been induced to promise her hand to a nobleman, when she suddenly hears the well-beloved sound of drums and trumpets. It is her own regiment with Tonio as their leader, for he has been made an officer on account of his courage and brave behaviour. Hoping that his altered position may turn the Marchesa's heart in his favor, he again asks for Mary, but his suit is once more rejected. Then he proposes flight, but the Marchesa detecting his plan, reveals to Mary that she is not her niece, but her own daughter, born in early wedlock with an officer far beneath her in rank, who soon after died in battle. This fact she has concealed from her family, but as it is now evident that she has closer ties with Mary, the poor girl dares not disobey her, and, though broken-hearted, consents to renounce Tonio.
The Marchesa invites a large company of guests to celebrate her daughter's betrothal to the son of a neighboring duchess. But Mary's faithful grenadiers suddenly appear to rescue her from those hateful ties, and astonish the whole company by their recital of Mary's early history. The obedient maiden however, submissive to her fate, is about to sign the marriage contract, when at last the Marchesa, touched by her obedience and her sufferings, conquers her own pride and consents to the union of her daughter with Tonio. Sulpice and his soldiers burst out into loud shouts of approbation, and the highborn guests retire silently and disgusted.