Act 1
It is carnival time in Venice. In a square near the Doge's Palace, a group of people are celebrating. Among them are the young lovers, Urbain and Agathe. Urbain is a French painter who has come to Venice to study. Agathe is the daughter of a Venetian senator. They are deeply in love, but their love is forbidden. Agathe's father has promised her hand to a wealthy nobleman, but she loves Urbain.
Urbain and Agathe decide to elope. They meet in a gondola and row away from Venice. However, they are soon caught by Agathe's father and his men. Agathe is taken back to her father's house, and Urbain is arrested.
Act 2
Urbain is taken to prison. He is visited by Agathe, who begs him to escape with her. Urbain refuses, knowing that he would only put Agathe in more danger.
Urbain is sentenced to death. On the day of his execution, he is given a last chance to confess his crimes. Urbain refuses, and he is beheaded.
Act 3
Agathe is heartbroken over Urbain's death. She decides to enter a convent. However, before she does, she goes to the prison where Urbain was executed. She sees his grave and places a flower on it.
As Agathe is leaving the prison, she sees Urbain's ghost. He tells her that he is finally free and that they will be together forever. Agathe is comforted by this, and she enters the convent.