Later that month, Jehan Frollo realizes that he has no more money and decides to go to Notre Dame to ask his brother, Claude, for enough money to get something to eat. He is sure that he will get a stern lecture from his Archdeacon brother but worries that he won't get any money. A priest tells him that Claude is in his cell and Jehan jumps at the opportunity to see his brother's secret hideout. Claude does not hear his brother come in and Jehan takes advantage of the situation to spy on him. The narrator compares the scene to a Rembrandt painting of Dr. Faustus, noting the eerie presence of skulls, globes, strange parchments, and magical inscriptions on the walls. Claude is mumbling to himself in Greek, Latin, and Hebrew, discussing different aspects of alchemy and trying to avoid thinking of La Esmerelda.
Jehan closes the door and pretends to have just entered his brother's cell. He asks him for money but Claude refuses, explaining how embarrassed he is at stories of Jehan fighting and drinking instead of studying. Jehan tries to pretend that he has been studying but an associate of Claude's approaches and Jehan is forced to hide under a furnace—but not before he forces his brother to pay him. Master Jacques Charmolue enters the cell and he and Claude begin discussing the laws of alchemy and their inability to turn light into gold. Jacques sees that Claude is not paying attention to him but is instead watching a fly get stuck into a spider's web. Suddenly an enormous spider rushes forward and kills the fly. Before they both leave the room, Claude warns Jacques not to "meddle with fatality."
On his way out of the cathedral, Jehan runs into Phoebus de Chateaupers. They are old friends and decide to go drinking together at a local tavern. They do not know that the Archdeacon is following them, sorely dismayed at Jehan's behavior and even more concerned that his friend is the same "Phoebus" that Pierre Gringoire had told him about. Indeed, Phoebus soon brags that he plans to meet La Esmerelda that same night. At the stroke of seven, they stumble out of the bar. As Jehan passes out in the mud, Phoebus goes to meet the gypsy dancer. Claude Frollo hides himself in a cloak and follows Phoebus instead of helping his brother. He soon recognizes that someone is following him and just as he turns around, catches Frollo's shadow creeping behind him along a wall. Worried at rumors of a goblin monk stalking the nighttime streets of Paris, Phoebus turns to confront his follower. Frollo does not reveal his identity but questions Phoebus about his meeting with La Esmerelda. The goblin monk grabs Phoebus and accuses him of lying. They almost fight but Frollo lends Phoebus some money on the condition that he can verify that Phoebus is telling the truth about his meeting with the gypsy dancer.
Phoebus agrees, and the two enter a nearby house. Just as La Esmerelda walks in the house, Phoebus hides Frollo in an adjoining room, which has a spy hole. La Esmerelda thinks they are alone and declares her undying love. Phoebus, who can hardly remember her name, pretends to love her just as much. He takes every opportunity to kiss her while Frollo gnashes his teeth in the dark. She is disappointed when Phoebus declares that he doesn't want to get married and refuses to let him touch her magic amulet, hoping that she will someday find her long lost mother. But when he declares that he thinks she no longer loves him, she pledges her entire soul to Phoebus, vowing to do anything he says for the rest of her life. Suddenly, a green monstrous face appears. La Esmerelda faints just as she sees an evil looking priest repeatedly stab Phoebus. When she awakens, she hears officers saying to one another that a "sorceress" has stabbed their captain.
The reader, along with Jehan, finally gets to peek inside Claude's secret cell and find out just how mad he has become. Claude only remains a priest by title and with the clothes he wears. He has rejected God and believes in only one thing: fatality. The recurring theme of fatality dominates this section, especially in the scene where Frollo watches a fly get caught in a spider's web. Many characters in the novel do not believe in free will. For example, when Pierre Gringoire follows La Esmerelda he "resigns his free will" and accepts any direction that she chooses. Similarly, Frollo believes that all actions have been predetermined and that nothing can stop him from catching La Esmerelda. Just as the fly was bound to get caught in the spider's web, he thinks that she is bound to fall into one of his traps. He thus uses this example of fatality to justify his actions, since nothing he or anyone else can do will change the predetermined outcome. As he warns his associate, one should never "meddle with fatality."
Hugo appeals to popular literary tastes of the early nineteenth century by emphasizing the theme of black magic and the supernatural. Surrounded by skulls and other tools of sorcery, Frollo is the stereotypical image of a priest gone bad. His attempts to turn air into gold show his abandonment of Christianity for the heresy of alchemy, but also indicate how far his obsession with La Esmerelda has taken him from reality. Indeed, watching Frollo mumble to himself in different languages and write spells on the walls not only represents a renunciation of God but also proves that he is no longer human. Moreover, Frollo easily fits into the mythical role of the "goblin-monk." We are left wondering if the rumors were not really about Frollo all along. He even continues to spy on La Esmerelda in the house, affirming the voyeuristic nature of their relationship. When he actually kills Phoebus, his green, demonic face shocks both lovers and his disappearance through an open window that looks out on the Seine makes him look more ghostly than ever.
The supernatural events in this section are all rationally explainable. Frollo is not really a goblin and none of his sorcery works. What makes these references frightening is Paris itself. As Phoebus turns to face the eerie shadow following him down a foggy and deserted Parisian street, we know that it is just Frollo. The suspense comes from the surrounding buildings and the ghostly feeling that seems to emanate from all directions. In effect, Frollo's cell and his magical incantations have no practical effect, but in the dark crevices of Notre Dame they acquire an outlandish and surreal quality that is fundamentally demonic. In scenes such as Phoebus's murder, Hugo's contemporary readers were unaccustomed to such violent imagery. The ghostly and supernatural quality of Frollo's character makes this grisly stabbing scene much easier to accept.