We encounter O’Brien in Book One, Chapter I, as he visits the Ministry of Truth. A large, burly man with a thick neck and a brutal face, an Inner Party member, he wears ominous if unfashionable black overalls. This authoritative man fascinates Winston.
O’Brien stands close to Winston and Julia during the Two Minutes Hate.
Winston dreams of O’Brien telling him: "we shall meet again in the place where there is no darkness."
O’Brien approaches Winston in the corridor at the Ministry of Truth and asks him whether he has seen the newest (tenth) edition of the Newspeak dictionary. When Winston says no, O’Brien gives him his address, inviting him to visit for a sneak preview.
O’Brien turns off the telescreen at his residence when Winston and Julia visit. They drink wine and chat about the Brotherhood. O’Brien inducts the two into the rebellious group.
O’Brien arranges for Winston to receive Goldstein’s manifesto, telling Winston that he will have fourteen days to read it. O’Brien dismisses Julia.
O’Brien nods when Winston asks whether the two will meet again in the place where there is no darkness.
O’Brien finishes the old rhyme about the bells of St. Clement’s that Winston starts.
O’Brien shakes Winston’s hand, and turns the telescreen back on as Winston steps out of his residence.
Along with other guards, O’Brien steps into the cell where Winston is kept.
Winston asks whether the Party has gotten O’Brien, too. O’Brien suggests he at one time was a rebel himself. Or not. We’re not sure.
After Winston is arrested, O’Brien orders a guard to beat Winston’s elbow with a truncheon. So begins Winston’s torture.
At O’Brien’s command, Winston is strapped onto a machine that is designed to stretch backbones until they break.
O’Brien physically tortures Winston, all the while re-indoctrinating him with the Party’s tenets. Winston becomes brainwashed, accepting whatever O’Brien tells him.
O’Brien tells Winston that mere acceptance of the Party is not enough, but Winston must truly believe. He must think like a Party follower. After the reintegration, O’Brien tells him that he will be released and ultimately executed.
After weeks or maybe months of torturing Winston, O’Brien asks whether Winston accepts the Party yet. When Winston says no, he forces Winston to look in the mirror for a picture of "humanity." It is not a pretty face.
Winston lashes back, and O’Brien recognizes that there is one last strength in Winston: Winston has not yet betrayed Julia.
O’Brien eases the torture on Winston for a few weeks until Winston acts out, and O’Brien sends him to Room 101.
O’Brien threatens Winston by showing him a cage of large, vociferous rats, waiting to gnaw away at Winston’s face.
O’Brien stands over Winston as his final spirit is broken; he betrays Julia. O’Brien clicks the cage door to the rats shut, satisfied that he at last has triumphed over Winston and free thought in general.