Juan Oliver wants to make a good impression at his new job as a prison officer and reports to work a day early, leaving his pregnant wife, Elena, at home. During his tour of the prison, an accident occurs that knocks him unconscious. He is rushed to the empty but visibly haunted walls of cell 211. As this diversion unfolds, convicts break free and hijack control of the penitentiary. Aware of the violence that is to come, the prison officers flee, leaving Juan stranded and unconscious in the heart of the prison riot. When Juan awakens, he immediately takes stock of the situation; in order to survive, he must pretend to be a prisoner.