In Messina in the 16th century the Sicilians celebrate victory over the Moors by the troops of valiant general Don Pedro, whom governor Léonato is about to receive. His daughter Héro awaits the return of her beloved Claudio with impatience, but her niece Béatrice taunts military valor, aiming her sarcastic remarks at another officer, Bénédict. The reunion is as tender between the engaged couple as it is stormy between Béatrice and Bénédict, who trade insults and mockery with a strange pleasure. When Claudio learns of his imminent nuptials from the general, he is as delighted as Bénédict is horrified. Don Pedro and Claudio conspire to lead the two enemies to also marry in accordance with the governor’s secret wish. Somarone, the music teacher, conducts his choir and orchestra for the evening festivity. His so-called masterpiece is given a rough handling by the choristers and rehearsed before a general not so keen on music. When the musicians have left, the general and Claudio start a conversation about Béatrice with the purpose of making Bénédict believe that she is madly in love with him. The young man eventually recognizes Béatrice’s qualities and decides to give up his pride and succumb to love. On her part, Héro had a similar discussion with her attendant Ursule and Béatrice overheard them. The night is falling with its share of promises.
In the governor’s palace, the banquet is in full swing and the cellar is soon empty. Already quite drunk, Somarone improvises a drinking song for the guests before the ceremony. Béatrice is tormented by her feelings but she eventually admits to herself that she loves Bénédict and that her aversion might have been fear to yield to love. Surprised and overjoyed to find a softened Béatrice, Héro and Ursule undertake to convert her to marriage. Before the wedding celebration, the two former enemies are on the verge of quarreling but Bénédict succeeds in stirring the defiant maiden. As the bridal procession enters, a second marriage contract is produced which hastens avowals: Béatrice and Bénédict get married… for the better and for the worse.