This Chapter is the ‘turning point’. It is when, for the first time, O’Brien speaks to him, refers obliquely to Syme, (who no longer exists or ever existed) and invites him to his flat to see the new dictionary of Newspeak.
The important points is that people don’t speak to each other in a corridor, they don’t ever mention someone who has been erased. And they never invite anyone to their homes.
Winston experiences this as proof of a ‘rebellion’ against the Party, while at the same time, a precursor to death.
Winston sees his faults; beginning with ‘thought crime’; that is thinking something which went against the Party. It was followed by the action of purchasing the Diary, and writing in it. Now he would visit O’Brien, whom he thinks has similar ideas.
He feels as if he is “stepping into the dampness of a grave…he had always known… was there and waiting for him.”