Ryu is a deaf-mute man who works in a factory. His ailing sister is in desperate need of a kidney transplant, but Ryu’s is not a match. After he loses his job, Ryu contacts a group of black market organ dealers to exchange one of his kidneys for one that his sister can use. However, the dealers disappear after taking Ryu’s kidney and money.
A legitimate kidney donor is found, but after having been conned by the organ dealers, Ryu is unable afford the operation. To raise money, Yeong-mi, Ryu’s radical anarchist girlfriend, suggests kidnapping the daughter of the executive that fired Ryu. They observe the executive with company president Park Dong-jin arriving at the latter’s home one day, where one of Dong-jin’s employees, Peng, attempts to commit harakiri in front of them. Ryu and Yeong-mi change their plan, deciding to kidnap Dong-jin’s young daughter Yu-sun.
Yu-sun stays with Ryu’s sister, who believes that Ryu is babysitting her. Ryu and Yeong-mi send a request for ransom to Dong-jin, and he obliges. Upon returning home with the ransom money, Ryu discovers that his sister learned that Yu-sun was kidnapped, and committed suicide.
Ryu takes Yu-sun and his sister’s body to a riverbed they frequented as children to bury her. Distracted by the burial and unable to hear, Ryu is unaware when Yu-sun slips into the river, and she drowns. After Yu-sun’s body is discovered by authorities, a deeply mournful Dong-jin hires an investigator to find her kidnappers. Dong-jin finds Ryu’s sister’s corpse by the riverbed, interacts with a mentally disabled man who witnessed Ryu burying his sister, and begins to piece together the identities of Ryu and Yeong-mi.
Ryu, armed with a baseball bat, locates the organ traffickers and murders them, receiving a stab wound in the process. Meanwhile, Dong-jin finds Yeong-mi and tortures her with electricity. She apologizes for Yu-sun’s death but warns Dong-jin that her terrorist friends will kill him if she dies. Unfazed, Dong-jin electrocutes her to death. Ryu returns to Yeong-mi’s apartment and sees the police removing her corpse.
Dong-jin knocks Ryu unconscious with a booby trap. He takes Ryu to the riverbed where his daughter died, dragging him into the water, slashing his Achilles tendons and waiting for him to bleed to death. After Dong-jin dismembers Ryu’s corpse, Yeong-mi’s terrorist associates arrive. They stab Dong-jin, pin a note to his chest with a knife, and leave him to die.