For what reason does Winston believe that O'Brien has talked with him? What are his feelings about this as the chapter ends?
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.
As Winston says, he had waited for this his entire life. He believes that O'Brien speaking to him is all about the existence of a real conspiracy, that he is going to be entered into the brotherhood or whatever it might be that is actually resisting the party.
In their brief conversation, O'Brien gives him his address, which Winston believes is the main point of their conversation. This way he can get to his flat where he may give him a message or he may leave a message in the dictionary of Newspeak which is the ostensible reason for his visit.
At the end of the chapter, Winston is terrified and excited at the same time, as though he has stepped into a new phase of his life that in some ways leads him inevitably closer to his grave.