People of Argratha who punish convicts by implanting memories of years of imprisonment, a sentence Miles O'Brien endured for a crime he did not commit.
Instead of keeping prisoners in real cells, the Argrathi use technology that implants a convict with memories of a long sentence in only a few hours. The experience feels completely real, and the prisoner leaves carrying the psychological scars of years that never happened.
In Hard Time, O'Brien was wrongly convicted of espionage on Argratha and lived through twenty years of false memories, including a cellmate named Ee'char. Back on Deep Space Nine he struggled with anger, isolation and guilt until Julian Bashir helped him confront what he believed he had done.