George Orwell’s 1984 is a dystopian novel of a future society that is controlled by Big Brother and the Party. In this society, people live under very strict rules that limit their freedom, thoughts, and ability to form emotional bonds with others.
O’Brien is a high-ranking member of the Party and is loyal to Big Brother. However, he is able to trick the novel’s main character, Winston Smith, into believing that he is a rebellious member of an opposition group called the Brotherhood. In so doing, he lures Smith and his girlfriend Julia into a trap and they betray the fact that they are disloyal to the Party.
When they are apprehended and taken to the Ministry of Love to be tortured and re-educated, O’Brien is the person who tortures Smith. He gives Smith a detailed explanation of the Party’s reasons for behaving as it does, and he (O’Brien) certainly appears to believe what he is saying. The fact that he doesn’t really try to justify the Party’s actions in moral terms tells us that he is unconcerned about right and wrong; he just wants to help the party maintain control by capturing people like Smith and forcing them to think the way the Party wants them to think.