Plot revealed below!
The aging Casanova is eking out a living as librarian to an absentee count. Encouraged by Edith, an innocent but curious servant, he begins reading extracts from his salacious memoirs. We learn of his unhappy childhood, his sexual awakening, and the adult Casanova's modus operandi in Venetian high society, where he acquires a servant, Rocco, and impersonates the ways of the wellborn in order to acquire money and seduce women. He meets an equally canny and upwardly mobile female version of himself in Henriette, with whom he falls madly in love. But she is engaged to Grimani, a jealous and conceited member of the nobility.
While pursuing the seducer's art, Casanova becomes intrigued by Bellino, a castrato whom Casanova is convinced is really a woman. He proposes; however his more lasting attachments have a way of not working out. While hearing Casanova's confession, a priest collapses from sin overload. Casanova nurses the cleric, Bragadin, back to health and is rewarded handsomely. Convinced that Henriette can now afford to ditch Grimani for him, our hero makes his move.
Continuing his reminiscences to Edith, Casanova relates the aftermath of his daring prison break from Venice, where Grimani was responsible for his incarceration. Accompanied by his young bastard son and Rocco, Casanova travels through Europe, searching for a sympathetic Venetian ambassador who will grant him a pardon so that he can return to Venice and Henriette. In Paris, he chances on Bellino. In London, he briefly glimpses Henriette herself and later trades insults with Grimani, who challenges him to a duel. In the exchange of pistol shots, he learns that Henriette loathes Grimani.
Wounded, Casanova travels to Saxony, where a mysterious nurse sent by an anonymous benefactor saves his life. A visit to Naples on the eve of an eruption of Vesuvius puts him back in touch with Bellino, who introduces Casanova to his previously unknown daughter, now grown up and irresistibly attracted to Casanova's grown up son.
The prospect of incest between brother and sister is too much for our hero, proving that he has standards after all. Years later, he laments to Rose his abiding love for Henriette -- concerning whose fate one last message arrives.