Fra Rinaldo’s worm-exorcism deception is a comic exposure of clerical hypocrisy and marital credulity: an affair concealed by religious office is made to look like a holy rescue, and the deceived husband rewards the supposed miracle-workers. In Elisa’s Day Seven story, the friar and his lover turn a child’s godparentage, prayers, and fear for an infant into the materials of a fraud that succeeds because the husband is anxious to believe.

Story and Narrative Frame

Elisa introduces the episode as another tale of conjuration, prompted by a preceding story about a phantom. The connection is deliberately comic: where one conjuration provides a precedent, Fra Rinaldo’s supposed rite becomes a cover for adultery. The episode is an embedded tale within the Decameron’s storytelling, narrated by Elisa to the company, rather than an event remembered by one of the people involved.

The story begins in Siena with Rinaldo, a young man of respectable family, passionately enamored of a beautiful neighbor, Madam Agnesa, who is married to a wealthy man. While she is pregnant, Rinaldo befriends her husband and offers to become godfather to the child. The offer is accepted. This new kinship gives him a respectable reason to speak with Madam Agnesa, but does not at first secure her agreement: when he discloses his desire, she is not displeased to hear it, yet his advance brings him no immediate success.

Rinaldo later becomes a friar. For a time, he sets aside his former love along with other vanities; in time, however, he resumes them without leaving the religious life. The narrator’s satire dwells on the contradiction between his habit and his appetites, presenting fine dress, elegant manners, and worldly accomplishments as incompatible with the sober discipline expected of a friar. When Fra Rinaldo again visits Madam Agnesa frequently and presses her, she objects that he is her child’s godfather and a monk. He answers by treating the religious impediment as removable with his gown, then argues that because her husband is more closely related to the child than the godfather is, and nevertheless sleeps with her, he may do the same. She accepts, or pretends to accept, this specious reasoning, and the two repeatedly meet under the very cover that godparentage had supplied.

The Locked-Room Deception

The decisive episode occurs when Fra Rinaldo visits and finds Madam Agnesa alone except for her little maid. He sends his companion with the maid to the pigeon loft to teach her the Paternoster, then enters the bedchamber with Madam Agnesa, who is holding the child. They lock the door and take their pleasure on a daybed. The arrangement turns religious instruction into a diversion for the only other person in the house who might interrupt them.

The husband returns unexpectedly and knocks at the chamber door. Fra Rinaldo has taken off his gown and scapulary and is dressed only in his waistcoat; both lovers recognize that the scene inside the locked room offers no easy explanation. Madam Agnesa quickly devises one. She dresses the friar, tells him to take the child in his arms, and prepares him to support her account. Then she opens the door and tells her husband that Fra Rinaldo’s arrival was providential: without him, she claims, their child might have died.

She says the baby suffered a sudden fainting fit and seemed dead. Fra Rinaldo, she alleges, recognized worms moving toward the child’s heart and undertook to conjure them away. The locked door, which might otherwise have exposed the lovers, becomes part of her explanation: only the child’s mother could be present during the rite, while the friar’s companion had to say prayers elsewhere because the husband could not be found. She presents the child as already restored and says Fra Rinaldo is waiting only for his companion to finish the prayers.

The Husband’s Belief and the False Miracle

The husband is so distressed by the thought that his child was near death that suspicion does not occur to him. Fra Rinaldo, having heard the explanation and dressed at leisure, completes the performance by calling the husband into the chamber. He hands over the healthy child and says that, only moments earlier, he thought the father would not see the child alive by vespers. He also recommends a wax image of the child, to be placed before the statue of St. Ambrose in thanks for the recovery.

The companion supplies a second, coordinated account. After keeping the maid occupied with prayers and giving her a small purse of white thread, he has listened unseen to what happened. Once the husband has accepted the story, he enters and reports that he has said all four of the prayers Fra Rinaldo assigned him. Fra Rinaldo replies that he himself had completed only two before Madam Agnesa called him, but that their combined efforts have pleased God and healed the child. The precise tally gives the invented rite the appearance of procedure, while the husband’s alarm makes him welcome its claims rather than test them.

Convinced that his child has been rescued, the husband weeps, embraces the child, and thanks Fra Rinaldo. He then serves the friar and his companion wine and sweets—the very hospitality that rewards their deception. He promptly has the promised wax image made and hung with the other offerings before St. Ambrose’s statue, turning the fabricated cure into a public token of gratitude.

Satire and Resolution

The deception succeeds through a chain of reversals. Fra Rinaldo’s office first gives him access to the household; when discovery threatens, the same religious identity lends authority to the fabricated exorcism. The lovers’ locked door is recast as a necessary condition of the rite, and the friar’s undress is concealed by the time the husband enters. The child, present throughout the encounter, becomes the apparent patient and the evidence of the supposed cure.

Elisa’s story makes the contrast between religious appearance and conduct its central comic instrument. Fra Rinaldo does not abandon his appetites when he takes the habit, and he uses religious language and ritual not to serve the household but to preserve his affair. The husband’s devotion to his child leaves him vulnerable: his relief overwhelms suspicion, and his gratitude supplies the fraudsters with food, drink, and an offering. The ending closes not with exposure or punishment but with the family’s wax image at the shrine, a devotional object founded on a false miracle. The final qualification that the statue was not the one at Milan sharpens the tale’s irreverent exit: the counterfeit wonder is attached to a particular local shrine, while the real marvel has been the ease with which adultery passes for sanctity.