Arturo comes to beg Alaide's forgiveness and confess his love, and, as he is about to enter the cabin, he encounters Valdeburgo, who again pleads with Arturo to desist in his attentions toward his sister, demanding that he draw his sword: (In an extended duet, first Valdeburgo —"Si...Sulla salma del fratello / T'apri il passo, a lei t'invia" / "Yes, over the corpse of her brother / Clear your way and approach her"—then Arturo—"Ah, pietà... non io favello; / È un amore disperato" / "Ah! have pity... It is not I who speaks; / It is a love that is desperate, / It is the grief of a wounded heart".) Arturo continues to describe the "torturing madness of a burning heart" while Valdeburgo explains that, for Alaide's peace of mind, Arturo must leave her in peace and that he should fulfill his promises to Isoletta by marrying her. Reluctantly, Arturo agrees to return to marry Isoletta, but asks that Alaide attend his wedding so he can see her one last time. Valdeburgo agrees.