In Part Two, Chapter Six, O'Brien approaches Winston and strikes up a conversation. For Winston, this moment is a significant one. Not only does Winston sense that O'Brien's "political orthodoxy was not perfect" (Part One, Chapter One), but he has also heard his voice in a dream. This phrase, "we shall meet in the place where there is no darkness," has become a symbol of Winston's resistance against the party.
After a few minutes of conversation on the topic of Newspeak, O'Brien gives Winston his address, on the premise that he can collect the newest edition of the dictionary. In Winston's mind, this meeting had only one purpose: "It had been contrived as a way of letting Winston know O'Brien's address." In addition, it provides the proof to Winston that "the conspiracy he had dreamed of did exist, and he had reached the outer edges of it."
While there is no doubt that Winston will "sooner or later...obey O'Brien's summons," Winston experiences a feeling of fear. This is because he knows that all rebels are found out eventually, as the text says: "The last step was something that would happen in the Ministry of Love. He had accepted it." Talking with O'Brien and taking the next step to outward rebellion is akin to "stepping into the dampness of a grave." It is a scary prospect which fills Winston with trepidation.
It is a tragic irony that Winston's sentiments in this scene foreshadow the events to come, long before he ventures to O'Brien's apartment. But Winston is right to be concerned for his future: he does, indeed, end up in the Ministry of Love and, even worse, in Room 101.