In the book's exposition, Winston has a dream that centers on O'Brien. This dream reflects the almost unexplainable hold that O'Brien has on Winston:
Years ago — how long was it? Seven years it must be — he had dreamed that he was walking through a pitch-dark room. And someone sitting to one side of him had said as he passed: ‘We shall meet in the place where there is no darkness.’
The idea of "meeting in the place where there is no darkness" is revisited in the novel. It is O'Brien's way of solidifying his hold on Winston. Given how O'Brien is a part of the Inner Party, he possesses insight and information that most do not. He is able to know the inner workings of Winston's mind to such an extent that he knows their paths are going to cross again because he knows what Winston is going to do. The phrase "meeting again in a place where there is no darkness" reflects how O'Brien is cognizant of how Winston's free will shall invariably lead to his destruction.
It is significant that the phrase of "meeting again" is repeated because it shows how O'Brien and the Party stand against free will. There is an inexorable pull on how the actions of individuals in Oceania will one way or another stand in the name of the Party. Individuals will willingly accept the power of the Party, an asserted realm where "there is no darkness," or they will be dragged into reeducation and forcibly accept it, in which case "there is no darkness." Either way, the repeated phrase reflects how much of a pull O'Brien has on Winston and how he knows what Winston is going to do. For his part, Winston does not fully understand the connection. He believes O'Brien's story that he is plotting with Goldstein. However, it becomes clear that O'Brien knows Winston's proclivity towards "thoughtcrime" and is simply waiting for him to commit to it and be taken to a place "where there is no darkness." In this regard, Winston's dream is almost prophetic as to what is going to happen to him.