On the 30th of September, the narrator's birthday, he waits in the vestibule of the brownstone for the postman, whom he hopes will be bringing money from his family. He runs into Holly, who invites him to go horseback riding as a last outing before she leaves to marry Jose in Brazil. She explains that she can't leave New York without saying goodbye to her favorite horse, Mabel Minerva.
The two take a taxi to Central Park. On the way, Holly explains that she will miss him, as well as Sally Tomato, who had warned her that the authorities suspected she was not his real niece. She tells him that O'Shaughnessy gave her $500 as a wedding present. The narrator, upset that she is leaving so suddenly, tries to tell her that she is already married, but she threatens to hang him if reveals that information and jeopardizes her marriage to Jose.
At the stables, Holly selects a sedate mare for the narrator, who is an inexperienced rider, while she mounts Mabel Minerva. As they ride across Central Park, the narrator is overcome with love for Holly, and realizes that his desire for her happiness is greater than his own need to keep her with him. This moment of exhilaration is cut short when a group of African-American boys leap out of the shrubbery and begin throwing rocks and taunting the horses. The narrator's horse rises on her hind legs and begins a violent gallop across the park and out into Fifth Avenue traffic.
Eventually, the narrator's runaway horse is brought to a halt by a mounted police officer and Holly, who has been following on Mabel Minerva. As a crowd gathers, the officer takes notes and arranges for the horses to be returned to the stables. Holly tells the narrator that he could have been killed, but he insists that he is only ashamed. When she kisses his cheek, however, he becomes dizzy and passes out on the sidewalk.
Back in his apartment, the narrator recovers in a bath while Holly sits on the edge of the tub, waiting to rub him with liniment. Sapphia Spanella knocks on the door and then enters, followed by two plain-clothes detectives, one male and one female. She points to Holly and identifies her as "the wanted woman". The female detective places her hand on Holly's shoulder and tells her kindly to "come along", but Holly warns her not to touch her, calling her a "driveling old bull-dyke." The officer slaps Holly, and the bottle of liniment flies from her hand and breaks on the floor. As Holly is escorted out of the apartment, she asks the narrator to feed her cat.
By that evening, the news of Holly's arrest is on all the front pages of the daily newspapers. To the narrator's surprise, the news had nothing to do with runaway horses; rather, Holly was implicated in a drug smuggling operation as an accomplice to Sally Tomato. O'Shaughnessy was also arrested, and revealed to be not a lawyer but a defrocked priest with a history of arrests for mafia activity. According to the press, Holly had been accused of acting as a liaison between Sally and O'Shaughnessy, conveying coded messages between the two men that allowed them to maintain control over a world-wide narcotics syndicate.
The narrator notices how the coverage distorts Holly's story for sensational effect, calling her a "movie starlet" when she was only an extra in films and claiming that she was arrested in "her luxurious apartment" when she was arrested in his own bathroom. One paper runs a story under the subheading "Admits Own Drug Addiction": while denying her knowledge of the narcotics ring to reporters, she admitted to having used marijuana. The papers also inform that narrator that despite her arrest, Holly remains unconvinced of Sally's guilt. "He's a sensitive, a religious person," she tells the reporters. "A darling old man."
Section 12 depicts the narrator achieving closure over his grief at Holly's sudden departure. Holly convinces the narrator to go horseback riding, marking the final appearance of horses as a recurrent motif in the novella. Holly associates horses with her brother Fred, stating that she imagined settling down with him in Mexico to raise horses. As Holly and the narrator ride alongside each other, they both experience an exhilarating high, and, seeing Holly's happiness, realizes that he loves her so much that he values her happiness above his own, even if that means the end of their friendship. By placing him on a horse, Capote subtly aligns him with Holly's brother Fred, a person with whom she felt safe and cared for. This association suggests the strength of the emotional bond between the narrator and Holly.
The section also sets the two characters up for contrast. Holly and the narrator's description of the horseback ride - "a glad-to-be-alive exhilaration" - echoes that of the mask theft at Woolworth's. The similar language links the two excursions and sets them up for comparison. As during the escape from Woolworth's, the narrator challenges his own boundaries and breaks habit by engaging in one of Holly's typically "carefree" activities. His pure happiness during both the theft and the horseback ride indicates that Holly's unconventional and spontaneous attitude is what is missing from the narrator's own life, and suggests that his attachment to Holly is partly a wish to become more like her.
However, while the Woolworth's theft ends smoothly, the horseback ride soon becomes dangerous, as the narrator's horse gallops into traffic and endangers his life. This near-tragic end to Holly and the narrator's last adventure serves two purposes. First, it confirms the bond between the two characters when Holly successfully halts the narrator's runaway horse, despite such vigorous riding endangering her pregnancy. Moreover, Holly's rescue of the narrator foreshadows the concluding events of the novella, in which the narrator helps Holly escape from the law.
Section 13 is a structural departure from the rest of the novella. Breakfast at Tiffany's is a linear narrative: events are told in the order in which they happen. In section 13, the order is reversed: the reader is told about the consequences of Holly's arrest before the arrest itself. Moreover, the majority of the section directly quotes newspaper coverage of the arrest. Up until this section, the events of Holly's life had been conveyed to the reader through the narrator. This switch of perspective violates the reader's expectations. Section 13's non-linear narrative and an external source of information is surprising, as it upturns the established method of the novella. Capote uses an unexpected structure that mirrors the shocking turn of events.
A central concern of Breakfast at Tiffany's is the impossibility of objectivity. Lies, gossip, and stories, all claiming to be true, play crucial roles in transmitting information between characters and shaping how they think about others and themselves. By quoting at length from the newspaper coverage of Holly's arrest, Capote demonstrates that even the purportedly "objective" information of the newspaper is itself prone to the same kind of errors, exaggerations, and biases as the "fictional" stories he writes, and the "fraudulent" tales Holly tells. For example, the narrator explains, Holly was arrested in his bathroom, yet the articles claim that she was found in her "glamorous apartment." The press distorts reality for its own purposes, as does Holly and, perhaps, the narrator itself. This section suggests that story telling is inherently subjective.