In the novel 1984 by George Orwell, Winston suspects that O'Brien is a member of The Brotherhood when he starts commenting on party issues in a very leading way. However, Winston has had suspicions before and detected a strange sort of independent spirit hidden within him and wonders whether deep down he actually opposes the party. The comments made by O'Brien simply serve to confirm his worst suspicions and they appear true to form. Winston finds this very disturbing and a bit scary but gets up enough bravery to approach O'Brien, saying he is an opposer of the totlitarian state. O'Brien tells him that as a member of The Brotherhood he wants to see the end of the party when actually it turns out he is a member of the Thought Police.
Scarily, it is almost impossible to do or say the right thing in this situation because there is so much double speak and many bluffs and double bluffs. The idea is to gain the confidence of 'traitors.' catch them and try to re-brainwash them to 'better ways of thinking.'