These lines in chapter 3:
He had seen her; he had even spoken to her. There was no danger in it. He knew as though instinctively that they now took almost no interest in his doings.
How did he know? And why had they stopped scrutinizing him?
There was no telescreen, but there must be hidden microphones: besides, they could be seen. It did not matter, nothing mattered. They could have lain down on the ground and done that if they had wanted to.
Before being sent to the Ministry of Love, Winston and Julia had been afraid of being caught together. But later Winston is not afraid and it seems like the Party is not interested in them either. Why?