It is revealed that Woo-jin, Dae Su's captor, was in love with his sister. Oh Dae Su saw the pair together and spread rumours. Woo Jin's sister thought she was pregnant and thus killed herself with the help of her brother Woo-jin. This is the reason Oh Dae su was kidnapped. Woo-jin tells Oh Dae Su the reason why he was released after 15 years: it turns out Mido (the girl Dae Su met at the restaurant after his release) is actually Oh Dae Su's daughter and Woo-jin had raised her in secret. Woo-jin had both Mido and Oh Dae Su hypnotised to fall in love. Dae Su begs to Woo-jin to not tell Mido the truth and he cuts out part of his tongue.
Woo-jin walks into the elevator and says, "My sister and I loved each other despite everything. Can you two do the same?" He then has a flashback wherein he is holding his sister over the river, in the same fashion Oh Dae Su held the suicidal man over the edge of the building. She takes Woo-jin's camera from around his neck to take a photo of herself, before he drops her into the river to die. When the flashback ends, Woo-jin kills himself via gunshot to the head. Oh Dae Su visits the hypnotist to erase the memories of what has happened. When Mido comes to him and hugs him, she tells him that she loves him. He forms a grin that would lead one to believe the hypnotism worked and he is now blissfully ignorant, but it then twists into a pained grimace which suggests otherwise. It is up for debate whether he remembers or not. Mido never finds out that she is Oh Dae Su's daughter, as Woo-jin allowed her not to find out.