The narrative rejoins Claude Frollo who, unable to stay and watch La Esmerelda die, ran off to the surrounding hills of the Université district. He does not realize that La Esmerelda is still alive. Left to himself, Frollo looks clearly into the shadows of his soul. He is horrified at having been responsible for the death of the woman he loves, while Phoebus, the only person he tried to kill, is still alive. Nevertheless, he still feels no guilt and breaks into a satanic laugh. He has become a demon, running from nature, God, science, and everything else he once believed in. He plunges into madness, convinced that skeletons are following him. He looks into a window and sees his brother, Jehan, with a prostitute. Aghast, he runs back to Notre Dame. Approaching his cell, he looks at a landing in an adjoining tower and thinks he sees La Esmerelda's ghost, not realizing that she is still alive.
La Esmerelda is horrified to see Quasimodo staring at her when she regains consciousness. She soon understands that he saved her but cannot fathom why. He brings her food and clothing, and comes to watch her while she sleeps. His presence frightens her at first but she tells him not to go. Quasimodo is hesitant, explaining that "the owl should never enter the nest of the lark." But he remains and they contemplate each other in silence, he seeing only beauty and she seeing only ugliness. They soon establish a routine, and La Esmerelda gets used to having Quasimodo stay close by. Even though he is deaf, he is never far, especially when she sings sad melodies. He calls her a "dew drop" and a "sunbeam" and promises to protect her. She begins pity him and they form an uneasy friendship.
La Esmerelda can still only think of Phoebus. Even though she knows he is still alive and that she was sentenced to hang for killing him, she does not blame him for not coming forward. Her love runs so deeply that she blames herself for her predicament, deciding that it was her fault for confessing. One day she sees him across the square and yells out to him. Phoebus doesn't hear her and Quasimodo offers to go fetch him. He waits the entire day in front of Fleur-de-Lys's house, not realizing that she and Phoebus are about to get married. When Phoebus finally leaves, Quasimodo asks him to come see La Esmerelda. Phoebus didn't know she had escaped and, thinking her dead, tells Quasimodo to go away. Quasimodo doesn't understand. However, since it was dark outside and La Esmerelda didn't see what happened, he tells her that he couldn't find Phoebus. She tells him to pay better attention next time.
Frollo doesn't know what to do when he finds out that La Esmerelda is still alive. At first he falls ill, and then he starts to spy on her and Quasimodo. He even grows jealous of the hunchback, imagining that the two of them have become lovers. Frollo finds the key to her room and sneaks up on her one night while she sleeps. She wakes up to his demonic face bent over her and cries out. Frollo begs her to love him. When she refuses, he grabs her and climbs on top of her. La Esmerelda finds a whistle that Quasimodo has given her. She blows it and the hunchback arrives within seconds. Because it is pitch black, Quasimodo grabs Frollo by the neck and starts to choke him without realizing who it is. Suddenly, the moon burst through the clouds and Quasimodo sees that he his choking his master. He immediately lets Frollo go. Frollo kicks Quasimodo aside and storms out of the cell, muttering to himself: "Nobody shall have her!"
Hugo's description of the different districts that made up Paris in 1482 serves as a backdrop in this section, as Frollo prowls the Université district. Now known as the Left Bank, this district was sparsely populated in the Middle Ages. Frollo is largely left to himself, wandering through pastures and small farm plots. Hugo uses this idyllic setting for both historical and stylistic purposes. Hugo carefully describes Paris's rapid urbanization since the 1750's. The idea of grassy meadows and farms in Paris would have been completely foreign to Parisians in the 1830's. This setting reinforces the historical focus of the novel by making readers in the 1830's realize how much the recent Industrial Revolution had changed Paris into a booming manufacturing town. The pastoral setting also evokes Frollo's complete break with the natural world. As he tears up grass and desecrates trees, he distances himself from everything that is human. Ironically, wherever Quasimodo goes, the elevated position of the Université district always keeps Notre Dame in his sight, stressing the cathedral as a geographical and moral center. Frollo can not escape this symbol of faith and compassion, which poignantly reminds him that he has lost all respect for humanity.
Hugo presents Quasimodo and La Esmerelda's friendship as a meditation on the meaning of beauty. Sitting together in the same room, they are on the complete opposite sides of the "spectrum of beauty." The most beautiful woman in Paris must look at the ugliest man in Paris, confronting the fact that beauty lies within. No matter how kind and generous Quasimodo is to La Esmerelda, she cannot help but recoil in horror each time she looks at him. In this sense, her confinement in Notre Dame not only cuts her off from the outside world, but also cuts her off from prevailing standards and prejudices of judging people based on their appearance. Each time she looks beyond the walls of the cathedral into the city, her old conceptions of beauty return. For example, when she sees Phoebus across the square, she cries out to him and declares that she loves him more than ever, even though she will die because of his cowardice and stupidity. Her feelings are based on nothing he has said or done, but only the way he looks. When she sends Quasimodo after him, the hunchback sadly realizes what it means to love someone in the real world: "Ah! I see. One must be but beautiful on the outside."
In the end, Quasimodo's downfall is due not to his ugliness, but to his inability to hear. When he waits in front of Fleur-de-Lys's house for an entire day, he can't hear the sounds of a wedding party going on inside. He thus doesn't realize what Phoebus is doing there and fails to grasp the urgency of the situation. When he finally confronts Phoebus, he can only guess what Phoebus is saying and assumes that he doesn't want to see La Esmerelda. In fact, Phoebus thinks she is dead and that Quasimodo is trying to trick him. Later, when Frollo attacks La Esmerelda, Quasimodo can't hear Frollo begging for mercy as he chokes him. Only a sudden burst of moonlight saves Frollo's life. This last scene represents Quasimodo's ultimate dilemma. He owes his life to Frollo but owes his soul to La Esmerelda. His deafness leads him to defend La Esmerelda at first, but we are left to wonder what would have happened if the hunchback had heard Frollo in the darkness to begin with.