Volume III, Chapter 1
Distraught by the loss of Agnes, Raymond is overcome by a terrible illness. This leads to a domino effect: Lorenzo is unable to ask Raymond to approve his marriage with Antonia, and because she hears nothing from Lorenzo, Elvira assumes that he must have found a new love interest. Elvira worries deeply about her daughter, often weeping when she imagines Elvira alone and friendless after her death.
Despite the loyal company of Lorenzo and Theodore (as well as the continued efforts of his servants to discover any trace of Agnes), Raymond falls deeper into illness and despair. Theodore especially makes numerous efforts to gain entry into the convent. One day, he disguises himself with an eye patch and pretends to be a beggar. Picking up his guitar, he reasons that if Agnes hears his voice singing outside the convent walls, he will know that his master has come to rescue her.
Theodore joins the ranks of beggars who come to the convent for free meals, and he charms the Porteress with his sweet voice and kind ways. Because he has no bowl or spoon of his own, the nuns say that they will offer him both in the convent, and invite him inside.
The Porteress feeds Theodore amply, and the rest of the nuns gather around to admire his youthful handsomeness. Theodore takes advantage of their attention to raise some questions about Agnes, but everything the nuns tell him only corroborate the Prioress’ story of Agnes’ last terrible illness.
The nuns decide that such a handsome young man would be a worthy addition to the Catholic Church, and intercede with the Prioress to allow him to take monks’ vows at the Monastery of the Capuchins. The Prioress says that she could certainly obtain this favor for him, and then departs.
Theodore continues to endear himself to the nuns by telling outrageous stories of his travels all over the world, his adventures among dog-headed men, and the incident that cost him his eye (gazing upon a nude statue of the Virgin Mary). He even sings them a song about a young woman who fell in love with a knight and dies from unrequited love.
The convent bell interrupts their little gathering – it is time for the nuns to return to their duties. The nuns beg him to return to the convent, and give him little gifts. An elderly nun named Mother St. Ursula gives Theodore a basket, and whispers “Agnes!” in his ear, just before the Prioress calls her away sternly.
Immediately Theodore brings the basket to Raymond, who is energized by this news of his beloved. Lorenzo is there as well. In the basket, the three men find a hidden note. The note tells them to obtain an order from the Cardinal-Duke to arrest both Mother St. Ursula and the Prioress during the festival of St. Clare next Friday; it warns the men not to make mention of these plans, which are the only possibility they have of honoring the memory of Agnes and punishing her assassins.
Filled with renewed grief now that he has solid evidence of the death of his beloved, Raymond falls back into despair. Lorenzo, however, is animated with fury, and vows vengeance on those who have unjustly killed his sister. Travelling quickly, he manages to obtain not only an order of arrest from the Cardinal-Duke (who is Raymond’s uncle) but also a letter to the principle officer of the Inquisition. He returns on Friday a few hours before the plan goes into motion, and solicits the help of his friends to confront the wicked Prioress.
However, the even more wicked Ambrosio is drawing closer to possessing Antonia, who feels an odd sense of dread for her daughter as night falls. She clings to her mother and kisses her, which puzzles Elvira, who is still recovering from her severe illness. Elvira kisses Antonia good night and goes to bed early.
Antonia sits at her window and listens to men playing love songs on their guitars. She thinks that one of them bears a strong resemblance to Lorenzo; in fact, it is Lorenzo himself, come to offer up a song to his beloved but bound by his promise to her mother not to visit her. Lorenzo sings a song about the affection of a youth for a young maiden, but Antonia is so modest that she assumes he intends this song for another woman. She says her prayers and goes to sleep.
At two in the morning, Ambrosio enters the house. The doors opens with a touch of the myrtle he holds in his hand, and he finds himself in Antonia’s bedroom. He lays the myrtle under Antonia’s pillow. Now that she is under his control, he takes a moment to watch her in her sleeping, helpless state: cheek upon one arm, covers thrown off, and hair arrayed over her pillow. Unable to suppress his lust, he begins to tear off Antonia’s clothes when he is interrupted by a scream.
It is Elvira. She was woken by a dream in which her daughter was about to fall into an abyss, and screamed to her mother to save her. Unable to sleep, she went to her daughter’s room just in time to see Ambrosio molesting Antonia’s sleeping form.
In fury, Elvira declares that she will unmask the wicked Ambrosio and reveal what a viper he truly is. She attempts to wake Antonia, but the demonic spell keeps her asleep. Ambrosio attempts to protest, begging Elvira to forgive him his transgressions and keep this nightly visit a secret. Elvira declares that she will do no such thing – after she is done revealing the truth, Ambrosio will never again falsely earn the trust of a parent. She screams for the servant. Ambrosio attempts to flee, but Elvira grabs his arm. The two struggle with one another, and Ambrosio grabs Elvira by the throat. Still weakened by her illness, Elvira struggles feebly. Ambrosio suffocates Elvira with a pillow from her daughter’s bed.
Seeing the corpse before him, Ambrosio is overcome with horror. He grabs the myrtle and flees the apartment.
Volume III, Chapter 2
Ambrosio is filled with horror and self-disgust – he has committed murder, the greatest of all sins. However, as several days pass, nobody discovers his crime. His guilt begins to die down, hastened by the advice of Matilda, who argues that he acted only in self-defense. Matilda further argues that either Ambrosio or Elvira had to perish, and that Elvira’s inflexibility and weakness made her a victim. Besides, she adds, now Antonia is completely undefended, and easy prey for the monk.
Ambrosio still lusts for Antonia, but now he despairs that he has lost his only chance to possess her. The enchanted myrtle is destroyed, and Ambrosio can only expect assistance from the demons if he asks for their help himself, which he is still unwilling to do.
Antonia, meanwhile, suffers terribly from grief. Upon waking in the morning, she stubs her toe on an object and is horrified to discover that it is her mother’s corpse. Her screams wake Flora, who finds Antonia clinging to her Elvira’s dead form. The landlady, Jacintha, arranges for Elvira’s funeral out of both kindness and base superstition (she does not want Elvira’s ghost haunting the house). Everyone assumes that Elvira’s death was a natural occurrence, since she endured convulsions during her recent illness.
Antonia is in a precarious and difficult situation. She is filled with grief at her mother’s loss and spends all of her days weeping; she is also completely alone in the midst of a large city, with very little money. She has been unable to reach the Marquis de las Cisternas, and she has heard nothing from Lorenzo. She thinks of calling on Ambrosio for help, but recalls her mother’s warnings about him.
At last, Antonia writes a letter to the Marquis de las Cisternas, but a series of unfortunate events prevent it from reaching him: Raymond has been caught up in the disappointment of losing Agnes, and has charged Lorenzo to give Antonia as much money as she needs, but Antonia will not speak to Lorenzo due to her mother’s orders. Thus, Antonia’s letter to the Marquis is returned to her unopened.
Antonia receives a letter from her aunt Leonella, who explains that she has married an apothecary and is returning to Madrid. However, the day of her arrival passes and still Leonella is nowhere to be seen. Antonia sits waiting by her window in the quiet night – there are no more youths playing love songs in the streets now that Lorenzo has gone to intervene with the Cardinal-Duke. Antonia wanders through the empty quiet house, and enters her mother’s room, picking up a book from the library. She reads a terrifying story about an inconstant lover punished by the ghost of her beloved, which only adds to her sense of dread.
Suddenly, the latch of the door is lifted up, and a ghost glides into the room. The linen-wrapped from says that in three days they will meet again, and Antonia beholds the face of her mother.
Antonia screams and faints. Her cries draw Dame Jacintha (the landlady of the house) and Flora. The two rouse her and Antonia explains that she has seen the ghost of her mother. At this, Dame Jacintha (a kind but very superstitious woman) goes into hysterics and runs to the domicile of the greatest holy man in Madrid - Father Ambrosio.
Ambrosio is unwilling to have an audience with this hysterical woman, but at the prompting of Matilda he allows her to make an explanation. Jacintha launches into a rather absurd story. A few Fridays ago, she claims, Elvira ate chicken; Elvira died not long after, and recently her ghost appeared lamenting her sin of eating chicken on a Friday.
Ambrosio is puzzled and annoyed by this outrageous story. However, he quickly realizes that this could be an excuse for visiting Antonia. He immediately goes with Jacintha to the apartment, under the pretense of offering an exorcism and counseling for Antonia.
Antonia is grateful to see the monk, since she considers him a good friend. Her mother did not clearly explain Ambrosio's dark intentions, and Antonia receives him warmly. However, the servant Flora (who knew Elvira's concerns about the monk) watches him cautiously. Antonia is so hard-hit by the shock of seeing her mother's ghost that a physician pronounces her near death. Ambrosio is somewhat distressed at hearing that the object of his lust might die, but Matilda counsels him. She explains that Antonia will indeed die in three days, but she will live long enough for Ambrosio to enjoy her.
Matilda goes on to say that Ambrosio must act quickly, for Lorenzo is planning to make Antonia his bride. She tells Ambrosio about a substance that will mimic death; he will give it to Antonia, fake her death, and then imprison her in the crypts under the monastery. There, he will be able to assault her without detection from the outside world.
Ambrosio is overjoyed by this plan. He asks Matilda how he can ever repay her, and she replies that he can offer his eternal friendship.
He hastens off to the apothecary of St. Clare's to obtain the substance. The monk is warmly welcomed into the apartment by Jacintha, and takes advantage of the momentary distraction of Flora to administer the substance to a very trusting Antonia. Ambrosio attempts to take his leave of the house, but Jacintha forces him to stay in case the ghost returns. Flora returns to her watchful position at Antonia's side.
At Jacintha's command, Ambrosio goes to sit in the room where Elvira's ghost appeared. He is consumed by panic that Matilda may have given him a poison to administer to her rival, and that Antonia might truly die. In this dark and gloomy state, he hears a strange noise, and notices that the closet door is unlocked. He looks at Elvira's bed, and ponders her terrible fate, imagining the rage of her ghost.
He catches sight of a figure in the alcove. Thinking that it is Elvira's ghost, he hesitates before rushing at it. He is shocked to discover it is merely Flora, who is overcome with embarrassment that she felt the need to spy on this respected monk. Ambrosio is giving Flora a lecture on the dangers of curiosity when Jacintha calls out that Antonia is dying.
Antonia is convulsing and groaning, and a doctor explains that she will die within the hour. With her "dying" breath, Antonia explains that she is grateful for Ambrosio's attention and kindness, and that she laments to leave him. She asks only that a mass be said in honor of her and her mother, using the little money they have left. Ambrosio gives her last rites, and Antonia - to all appearances - dies.
Jacintha frets about the possibility of a second ghost haunting her apartment, and Flora weeps uncontrollably. Ambrosio surreptitiously checks Antonia's pulse, and finds it still beating weakly. Flora accepts Ambrosio's generous offer to inter Antonia's body in the sepulcher of St. Clare's, and Ambrosio takes it with him.
Later that day, Leonella arrives in Madrid with her young husband. She is deeply grieved when she learns that her sister and niece have passed away, but there is nothing more she can do for them, so she returns to Cordova.
The anti-Catholic themes in the novel become especially pronounced at this point. Lewis suggests that monasteries are fill of hypocrisy-veiled lust; Ambrosio and Matilda conduct a black mass in the crypt of a monastery. During Theodore's visit to the convent, Lewis emphasizes the credulous and innocent nature of the nuns: they are willing to believe anything that Theodore tells them, even if it goes against common sense. The cryptic note left by Mother St. Ursula suggests even worse vices plague the convent.
Ambrosio's depraved nature also becomes truly clear - he not only elicits demonic assistance in his mission of raping a young woman, but he also kills her mother when she tries to protect her child. Ambrosio cares nothing about the wellbeing or happiness of the young woman he claims to love; he only wishes to take what he wants from her.
The differences between the characters of Lorenzo and Ambrosio are well-illustrated by their opposite reactions to Elvira's order to stay away from Antonia. When Elvira asked Lorenzo to stay away from her daughter, he obeys her wishes despite his protestations that he planned to make her daughter an honest women; he only comes close to breaking these vows when he sings love songs under Antonia's window at night. Ambrosio, on the other hand, is opaque about his designs regarding Antonia, and when Elvira steps in to protect her daughter, Ambrosio kills her.
The use of the myrtle draws on eighteenth century plant symbolism: the myrtle was a symbol of marital happiness, often carried by brides. In the novel, the myrtle is also related to sexuality, though it is twisted and distorted. It is used in the service of violent lust, not marriage, and a wicked monk, rather than a bride, carries it.
Jacintha's explanation for Elvira's ghostly appearance draws on elements of Catholic practice. Eating meat on Fridays is forbidden in Catholicism - good Catholics are required to eat fish on this day. Jacintha's wholehearted endorsement of this rule (and her assumption that Elvira would be relegated to eternal punishment for breaking it) emphasizes her superstitious and foolish nature.