Vivaldi falls madly in love with Ellena when he sees her and her aunt walk home from church one day, but Ellena is just some orphan with only a small villa in Naples, while Vivaldi is the only son of the Marchese, who cares more for his family’s honor than for anything else, and the Marchesa, who more than that even cares for money. The Marchese forbids it, and the Marchesa goes a bit farther. Schedoni, a monk and her confessor, plots with the Marchesa to have Ellena murdered. She’s abducted and taken across the country to the monk’s usual murder site, but just as he draws the stiletto, he see’s a miniature portrait of himself around her neck and realizes she’s his daughter.
Vivaldi, meanwhile, has arrested by the Inquisition on charges trumped up by Schedoni. It looks bleak, but then a strange friend appears in the form of a monk who might also be a ghost — Vivaldi is half of that opinion until he appears to the others at the tribunal. He delivers a strange tale of intrigue: Schedoni murdered his brother, the Count di Bruno, so that he could marry his wife, but believing her to be unfaithful to him, killed her in a jealous rage. At the confessional, he told of his crime to the monk Anslado — who, turns out, was the very man he suspected she was unfaithful with. Spalatro, Schedoni’s accomplice, on his deathbed confessed this to Nicola di Zampari — Vivaldi’s ghostly monk.
I’ve left out numerous subplots, one of them introducing a nun called Olivia, who it turns out is actually Countess Olivia, Ellena’s mother (who’s less dead than Schedoni believed). She and Schedoni did have a daughter, but she died in infancy. Ellena’s father was the murdered Count di Bruno. Schedoni never learns his error, though, as he poisons himself (and Nicola) in prison rather than face execution. Vivaldi is freed. With Ellena now known to be of noble blood, the Marchese consents to her and his son’s marriage. The Marchesa previously died in a subplot I omitted.