After being caught by the Thought Police, Winston Smith is taken to Room 101, the torture room where physical and psychological torture is employed. It is a white porcelain room that is windowless with a high ceiling. The room is flooded with light from hidden lamps, and a low, humming sound permeates; there is a bench and a lavatory and four telescreens in this barren room. O'Brien enters and begins Winston's "correction." This involves physical and psychological torture.  O'Brien answers some of Winston's questions, but will not tell him if Big Brother exists. 

After electric shock is applied to Winston, O'Brien asks Winston, "What country is Oceania at war with?" Winston replies that he does not remember. He says this because he knows it is always at war with Eurasia or Eastasia so that it will keep people at "peace"--War is Peace. Oceania stays at war because doing so keeps the people united against an enemy. Later, O'Brien asks Winston how many fingers he holds up and Winston replies correctly. Then, O'Brien only holds up four, but tells Winston there are five. Winston agrees even though he sees only four; defeated by the torture, Winston resists more electric shock. Still, Winston remembers the truth as

one remembers a vivid experence at some remote period of one's life when one was in effect a different person.

At the end of Chapter II of Book Three, Winston asks O'Brien what is in Room 101. "Everyone knows what is in Room 101," O'Brien replies as a needle goes into Winston's arm. In Chapter III, O'Brien tells Winston that his "reintegration" is to begin. After his conversion through torture, Winston wakes one morning and calls out Julia's name; it is then that he is taken to Room 101 because his emotional "progress" has not been complete. In Room 101 the enemies of the state are converted completely because it addresses the enemies' basic fears.

Room 101 is "the worst thing in the world." For each individual, this "worst thing" is what that person dreads the most. Pain is not enough; it must be "the unbearable" O'Brien explains.

"There are occasions when a human being will stand out against pain, even to the point of death. But for everyone there is something unendurable--something that cannot be contemplated. Courage and cowardice are not involved.

For Winston, the rats are the "unbearable." When O'Brien tells Winston that he will release the rats onto Winston's, face, Winston betrays Julia, screaming that she should be subjected to this torture, not he. Satisfied that Winston has relinquished his emotional attachment to Julia, he puts away the cage of rats.