The story takes place in Ravenna and Rimini.
Francesca, daughter of Guido I da Polenta, for state reasons, is to be married to Giovanni, known as Gianciotto, the malformed son of Malatesta de Verrucchio. But as Francesca would certainly refuse to marry the lame and deformed Gianciotto, she is introduced in the first act, by means of a well-laid plot, to his handsome younger brother, Paolo, known as il Bello. Under the impression that Paolo is her destined bridegroom, Francesca falls deeply in love with him at first sight; he also falls passionately in love with her, although they do not exchange a single word.
The next act shows a fight in progress between the Guelphs and Ghibellines, and on the platform of a tower of the Malatesti, Francesca, now married to Gianciotto, meets Paolo and gently reproaches him for the fraud practised on her. He protests his innocence of the plot and reveals his intense passion for her. Gianciotto brings the news of Paolo's election as Captain of the People and Commune of Florence. Paolo departs for Florence.
In the third act Francesca, in her luxurious apartment, is reading the story of Lancelot and Guinevere to her women. They then dance and sing in celebration of the advent of Spring, until, on a whispered word from her slave, Francesca dismisses them. Paolo, sick with longing for her, has returned from Florence. He enters; they continue reading the story of Guinevere together, until, no longer in control of their feelings, they let their lips meet in a long kiss.
In the fourth act Malatestino, Gianciotto's youngest brother, who himself lusts for Francesca, has discovered her secret meetings with Paolo. After Francesca refuses to give in to his sexual advances, Malatestino betrays Francesca and Paolo to Gianciotto, who determines to find out the truth for himself. Accordingly, Gianciotto lies in wait outside Francesca's door, and surprising her and Paolo together at early dawn, he slays them both.