91. Hard Time
Summary
O'Brien has been in a horrible prison for twenty long years. Suddenly he wakes, and learns that those twenty years never happened. He was on a mission to Argratha when his technical curiosity led to his being convicted of espionage and subjected to an experience of prison, fed into his brain. Back on DS9, O'Brien tries to readjust to his old life, but is plagued by memories of his imaginary cellmate and friend, Ee'char. He nearly commits suicide, but is stopped by Bashir. O'Brien finally tells Bashir that he killed Ee'char over some bits of food that he then found out Ee'char planned to share. Having spoken of Ee'char, he can now recover.
Summary provided by The DS9 Encyclopedia and Lexicon by kind permission of Tracy Hemenover.