Part three opens with a turn back to Juvenal Urbino as a young man. He is returning from a long stay in Paris studying medicine, and he is returning as a very eligible bachelor. While in Paris, he remembered his home with deep nostalgia and longing, believing that it was the best city in the world. Upon his return, however, he finds that he was blinded by his nostalgia. He is so disillusioned by the reality that everything seems almost worse than it actually is. His own home--and his mother--have fallen into gloomy decay. He slowly accustoms himself to the state of his city, but he begins a lifelong effort to improve it.
He begins by taking over his deceased father's office and introducing the modern medical ideas he learned in Paris to the Misericordia Hospital. This intervention earns resentment from his colleagues. He also becomes obsessed with the serious and dangerous sanitation problems in the city, and he tries to force the government to improve the conditions. These conditions probably were tied closely to a horrible cholera epidemic that occurred while Urbino was in Paris. The epidemic caused the highest death toll in the city's history, and Juvenal's father, Dr. Marco Aurelio Urbino, became known as a civic hero for all the attention he gave to the epidemic. The elder Dr. Urbino contracted cholera himself and died in quarantine in order to protect those he loved.
Considering his father's death, Dr. Urbino becomes obsessed with cholera and learns everything he can. Less than a year after his return, cholera cases start popping up, but an epidemic never recurs. Everyone is convinced that this is because of Dr. Urbino's strict sanitary rules, which makes Juvenal able to convince the City Council to implement new sanitary guidelines. It is a victory, but he is too distracted to relish it for he has met and fallen for Fermina Daza.
He met her when a colleague called him to consult due to Fermina's possible symptoms of cholera. Dr. Urbino examined her under Lorenzo Daza's watchful eye, and he showed no signs of emotion at the time. Fermina thought he was too self-important to notice her. But he returns a few days later unnecessarily and without an appointment. He examines her through the window during her painting lesson, but she rudely turns him away. Lorenzo calls out to Dr. Urbino, but he is not angry so much as apologetic for his daughter since Dr. Urbino is exactly the kind of man Lorenzo wants her to marry.
Dr. Urbino continues trying to woo Fermina while Lorenzo tries to soften her to his attempts. At the same time, Lorenzo and Dr. Urbino each try to woo the other. Dr. Urbino sends a letter to Fermina, and it is so simple and serious that her rage against Urbino immediately disappears although she does not respond to it except to burn it. Dr. Urbino continues to send her letters, two weeks apart, but she still does not respond. She starts to receive threatening objects and letters containing accusations of her having bewitched Dr. Urbino. Dr. Urbino goes so far as to send Sister Franca de la Luz, who expelled Fermina, to convince her to marry him. She does not accept.
Hildebranda comes to visit Fermina to convince her to accept Dr. Urbino. Hildebranda goes to see Florentino, who does not know who she is but who helps her send messages to her own love. Fermina gives Hildebranda tours of all the sites of her relationship with Florentino. Hildebranda tries to increase the excitement in Fermina's life, and they go together to a Belgian photographer. When they leave his studio they are dressed inappropriately, and Dr. Urbino in his landau saves them from being publicly humiliated in the street. After this fateful ride Dr. Urbino reminds Fermina that he is still waiting for her answer, and she finally writes him a letter allowing him to speak to her father.
When Florentino discovers that Fermina is to marry Dr. Urbino, he becomes inconsolable. Transito persuades his uncle, Don Leo XII Loayza, to give him a job that will remove him from Fermina, over twenty days' travel away. Florentino serenades Fermina one last time, then embarks on one of his uncle's riverboats to leave home for the first time. Florentino is forced to yield his cabin to the new plenipotentiary from England, who joins the boat at the last minute. The journey is difficult, but Florentino endures it as he endures everything, and he speaks to no one.
One night on the boat as he is walking to the toilets, a woman pulls him into her cabin suddenly and makes love to him, taking his virginity. He never sees who she is, so he becomes obsessed with determining her identity. He narrows it down to three companions and decides arbitrarily that it was Rosalba, a young mother. He becomes obsessed with her. She and her companions leave the boat eventually, and he again becomes very depressed about Fermina. He imagines their wedding and honeymoon with such vividness that he becomes ill, and the captain, worried that he has cholera, quarantines him for the night. He wakes up happy for he has decided to stay on the boat on its return trip to his city, and the captain allows it since he gave up his cabin on the first half of the journey.
Upon coming home he learns that Fermina has gone to Europe on a honeymoon. He considers how to replace her in his life. One night his mother offers refuge to the Widow Nazaret as a ploy to cure her son of his love for Fermina. They make love, and this is the start of a long but uncommitted relationship, including profligacy for both. Nazaret's name is the first to be entered in Florentino's notebook titled "Women," which by the end of his life has six hundred twenty-two entries listing his long-term liaisons.
For almost two years Florentino believes that he has survived the torment of losing Fermina Daza--until he sees her again for the first time, leaving High Mass on her husband's arm, more beautiful than ever, and six months pregnant.
Fermina had entered marriage a virgin, terrified about her future. She was so terrified that she barely noticed the continued threats and accusations she received anonymously from the upper-class society she was about to enter. Her lack of reaction fortunately caused the authors of these notes to accept her. The loss of her virginity was slow and painless. Their first kiss in Europe had led Dr. Urbino to believe that he would grow to love her, and now that they are home, it is not clear whether it is their love or Europe that has changed them.
Part three is the section of the book that is most preoccupied with class. It remains secondary to the theme of love, but it is closely tied to the marriage that takes place between Dr. Urbino and Fermina. The threatening letters that Fermina gets from anonymous upper-class authors get equal if not more attention than the letters that Dr. Urbino sends to Fermina in the quest for her hand. Indeed, the fact that the descriptions of their wedding are focused almost solely on the issues of Fermina's integration into Dr. Urbino's class highlights the lack of love that is present at the time of their marriage. It should not be on the honeymoon that the groom realizes he might grow to love the bride.
Again the issues of love are never simple. Fermina, though cold and reserved as usual, shows signs of being obsessed with Dr. Urbino. And although the narrator tells us that Dr. Urbino only marries Fermina for her haughtiness, he is obsessed by her enough that his feelings distract him from the accomplishment of his professional goals. The marriage has a great deal to do with the influence of Fermina's father, once again suggesting her limited agency in the relationship. If Dr. Urbino and Fermina have found love in Europe, we have only the narrator's account to trust, seeing only glimpses of this time period and hearing none of the dialogue between Fermina and Dr. Urbino.
This part also complicates the theme of love with its incorporation of sexuality. The narrator conflates Fermina's and Urbino's sexual intimacy almost completely with love, paralleling their growing sexual comfort with each other with a growing love--and never making a clear distinction between the two. Fermina thinks so much about her obsessive fear of the wedding night that she can barely function at the wedding. The ritual of love is dominated by apprehension of sex.
Florentino also has quite an introduction to sexuality in this part. He has become an inconsolable and unrequited lover. Somehow his first sexual encounter is shrouded in mystery. He soon finds pleasure, distraction, and even some form of love in his sexual encounters with the Widow Nazaret, soon to be followed by hundreds of others. This is the start of Florentino's use of sex as a proxy for love, a pattern that lasts until Dr. Urbino's death. But with Rosalba (if she is the one) and Nazaret, he does feel something more than simply physical pleasure, so in these relationships of Florentino at least, sex is not totally separable from the love he lives for.
Florentino's sexual escapades have a double, contradictory set of functions. On the one hand, he has 622 long-term liaisons, suggesting the weakness of his commitment and his new view of respect for women. Whereas Fermina's trip helped her mature, Florentino's aborted trip gave him new sexual knowledge and led him into a life of profligacy. Yet, these escapades are not characterized by the love he continues to hold for Fermina, which shows the strong power of his love. These escapades will never add up to a replacement for his love for her, because this love is of a different order. While Florentino seems to love, on some level, many of the women he sleeps with, his pattern of love continues to lack the depth that one would expect in a more mature and responsible man--compare his love letters to the letters sent by Dr. Urbino--and it remains unclear what extra feeling he really has for Fermina.