One day, Julia secretly hands Winston a note saying she loves him, and the two begin a torrid affair; an act of rebellion as the Party insists that sex is only for reproduction. Julia shares Winston's loathing of the Party, but he realizes that she is politically apathetic and uninterested in overthrowing the regime, thinking it impossible. Initially meeting in the country, they later meet in a rented room above Mr. Charrington's shop. During his affair with Julia, Winston remembers the disappearance of his family during the civil war of the 1950s and his tense relationship with his wife Katharine, from whom he is separated (divorce is not permitted by the Party). He also notices the disappearance of Syme during one of his working days. Weeks later, Winston is approached by O'Brien, who invites Winston over to his flat, which is noted as being of far higher quality than Winston's. O'Brien introduces himself as a member of the Brotherhood and sends Winston a copy of The Theory and Practice of Oligarchical Collectivism by Goldstein. Meanwhile, during the nation's Hate Week, Oceania's enemy suddenly changes from Eurasia to Eastasia, with no-one seemingly noticing the shift. Winston is recalled to the Ministry to help make the major necessary revisions of the records. Afterwards Winston and Julia read parts of the book, which explains more about how the Party maintains power, the true meanings of its slogans, and the concept of perpetual war. It argues that the Party can be overthrown if proles rise up against it. However, to Winston, it does not answer 'why' the Party is motivated to maintain power.
Winston and Julia are captured and imprisoned when Mr. Charrington is revealed to be a Thought Police agent. At the Ministry of Love, Winston briefly interacts with colleagues who have been arrested for other offences. O'Brien arrives, revealing himself as a Thought Police agent, who tells Winston that the Brotherhood does not exist and Emmanuel Goldstein's book was written collaboratively by O'Brien and the Party themselves as part of a special sting operation to catch thought-criminals. Over several months, Winston is starved and tortured to "cure" himself of his "insanity" by changing his own perception to fit in line with the Party. O'Brien reveals to Winston that the Party "seeks power for its own sake." When he taunts Winston by asking him if there is any humiliation which he has not yet been made to suffer, Winston points out that the Party has not managed to make him betray Julia, even after he accepted the party's invincibility and its principles. Winston accepts internally that he really means he has not rescinded his feelings toward Julia; he betrays her by revealing her crimes many times. He fantasizes that moments before his execution his heretic side will emerge, which, as long as he is killed while unrepentant, will be his great victory over the Party.
O'Brien takes Winston to Room 101 for the final stage of re-education, which contains each prisoner's worst fear, indicating that the level of surveillance on the public is far more thorough than initially believed by Winston. Confronted with a wire cage holding frenzied rats, his biggest fear, in his face, Winston willingly betrays Julia by wishing the suffering upon her instead. Winston is released back into public life and continues to frequent the Chestnut Tree Café. One day, Winston encounters Julia, who was also tortured. Both reveal that they have betrayed the other and no longer possess feelings for one other. Back in the café, a news alert sounds and celebrates Oceania's supposed massive victory over Eurasian armies in Africa. Winston finally accepts that he loves Big Brother.