On what pretence does o'brien want to meet Winston? How does Winston feel?

O'Brien bumps into Winston in a hall. He says that he has a copy of the new Newspeak dictionary( 11th edition I think) and wants to consult Winston about it. Winston is both terrified and excited. His wild hunch that O'Brien is part of the "Brotherhood" might just be true. At the same time Winston could just be being set up to be vaporized like Syme was.