Vincentio di Vivaldi becomes infatuated with a woman named Ellena di Rosalba, whom he sees while attending service at the Church of San Lorenzo. He follows her and her elderly companion, Signora Bianchi, later revealed to be Ellena’s aunt. Seeing an opportunity to escort the two women to their home, Vincentio offers Signora his arm to help her walk.

He revisits the villa in hopes of seeing her but is unable to do so. That night, he is wandering through a garden when he is approached by a ghostly figure in monk’s clothing. This figure tells Vivaldi to be wary of visiting the villa again in the future. Due to his love for Ellena, he continues to visit anyway, spurring another visitation from the ghostly figure. Although he doesn’t find out who this ghostly figure is, Vivaldi decides to bypass the warnings by asking for Ellena’s hand in marriage.

Signora Bianchi is initially hesitant at the prospect of marriage but eventually comes around to giving Vivaldi and Ellena her blessing. Vivaldi’s parents, however, are not as supportive. Vivaldi’s mother calls on monk Schedoni to prevent the union of Vivaldi and Ellena.

Signora Bianchi is killed via poison, and Ellena must seek sanctuary at the convent of Santa Maria della Pieta after the funeral. While making preparations, Ellena is suddenly abducted by three masked men and thrown into a closed carriage. She is brought to a convent where she is placed in the care of nuns. Vivaldi, concerned for her safety, goes to the villa to find a servant tied to a pillar and learns about the abduction. Convinced that these strange events may be planned to prevent his marriage, Vivaldi decides to track down the closed carriage.

During his search, Vivaldi comes across a group of pilgrims on their way to a shrine and travels with the group until he arrives at the service Ellena is attending. Disguised as a pilgrim, Vivaldi passes a note to Ellena telling her to meet him later at the gate. They manage to escape and go into hiding as they attempt to escape their pursuers.

Schedoni eventually tracks them down as they almost get married at a chapel and are arrested by warrant of the Holy Inquisition. Ellena is charged with abandoning her duties as a nun, and Vivaldi is charged with aiding her escape. He is imprisoned in Rome, waiting for a future trial.

Schedoni, who is determined to kill Ellena, sneaks into her room and readies his dagger over her sleeping body. He notices a miniature worn around her neck. Ellena is awakened and Schedoni asks about the miniature. When she answers that the miniature is of her father, Schedoni is disturbed at the possibility that he almost killed her daughter.

Schedoni tries to make amends by convincing Vivaldi’s mother to approve of the marriage but is rejected. He then decides to officiate the wedding himself. After a hearing before the tribunal of the Inquisition, Vivaldi is approached by a strange monk who tells him to reveal the true identity of Schedoni to the Inquisition. Vivaldi follows these instructions, and Schedoni is arrested on his way to Rome.

At the trial, much is revealed concerning Schedoni’s history and his involvement with the two lovers. Once known as Count di Marinella, he had his brother assassinated in order to gain his title, estate, and wife. The ghostly figure that visited Vivaldi is revealed to be Father Nicola, who gathered evidence against Schedoni. Schedoni administers a deadly drug to Nicola but dies of the same drug himself. Because of his confession, Vivaldi is set free and is finally able to marry Ellena.