What is the climax of this novel?

The climax of this novel was when everything was flipped. Winston and Julia gets caught by Mr. Carrington's treachery, O'Brien was actually involved in thought police, and Winston and Julia gets brainwashed. I was very shocked when I knew Mr. Carrington betrayed them! Though I thought O'Brien was suspecious, Mr. Carrington was just a shock. Its like a close friend who knows your secret blows it all to others! I felt there is no one else we can trust except God. O'Brien was a person who I did not trust at the first place when Winston and Julia went to him. I felt hopless again as Winston and Julia were being brainwashed. Winston and Julia are just poor, miserable people who are caught and get tortured. I was depressed because there are being tortured and brainwashed for holdfasting the truth.
It was depressing when the ending was not the ending I expected. The climax part made my heart pound and heartwrenching for they had to lose their love, thought, and truth.