This chapter relates how, after a series of incredibly disturbing beatings, Winston is completely broken and has confessed to everything that he has been told he needs to confess to. But at the same time, his process of rehabilitation, if that is what you want to call it, is not over yet. It is obvious that he still has some way to go, and as he hears the voice of O'Brien, it is clear that O'Brien recognises this too:
Don't worry, Winston; you are in my keeping. For seven years I have watched over you. Now the turning-point has come. I shall save you. I shall make you perfect.
O'Brien then goes on to torture him with a machine that causes pain. Through this special torture session, O'Brien challenges Winston's notion of the truth, and argues that the only truth that exists is what the Party says is true, even if that were 2+2=5. O'Brien thus tries to show Winston the truth of one of the Party's statements:
Who controls the past controls the future: who controls the present controls the past.
Thus it is that the Party can change history to suit its own needs and can manipulate the truth so that it can control the present, future and past. Finally, after Winston's desperate attempts to cling on to what he thinks is the truth, he is taken to Room 101 and the chapter ends.