Oldboy's success rides firmly on the back of its balls-out commitment to being sick and depraved. It is a tale of vengeance marked by the utterly grotesque and the downright viscerally affecting and the ending twist creeps up on you like a sledgehammer. In a sudden turn of events that could not have been foreseen, the film's lead Dae-su realises he went to school with his tormenter Woo-jin, and witnessed an incestuous relationship between Woo-jin and Woo-jin's sister. Dae-su had revealed this information before relocating, unaware the two were siblings and Woo-jin's sister committed suicide as a result. The cherry on top of the entire scenario is the fact that Woo-jin reveals that Mi-do - the woman he has been enjoying a romantic relationship with since his release - is actually Dae-su's daughter, who was four at the time of Dae-su's abduction and imprisonment. Wishing for Dae-su to feel the same torture he felt when his sister died, Woo-jin plans on revealing the truth to Mi-do in hopes that she takes her own life as well. In order to keep the truth hidden from Mi-do, Dae-su cuts off his own tongue as an act of atonement, which Woo-jin accepts before taking his life as promised. The act of atonement is one that is fitting as Mr. Park, the warden of the prison, had initially informed Woo-jin that he was imprisoned for "talking too much."