Cha Tae-sik is a quiet man running a pawnshop. His only friend is a little girl, So-mi, who lives in the same neighborhood. So-mi’s mother, Hyo-jeong, is a go-go dancer and heroin addict.
Instructed by her lover, Hyo-jeong steals a large pack of heroin being sold at the bar where she works, hides it in a camera bag which she pawns to Tae-sik for safe keeping. Her action attracts the attention of Crime lord Oh Myung-gyu, who tasks his subordinates, brothers Man-Seok and Jong-seok, to retrieve the drugs. Jong-seok locates Hyo-jeong, tortures her in front of So-mi, and forces her to reveal where the drug is. His lackeys, Du-chi and Bear, go to Tae-sik’s place to intimidate him, but he easily overpowered them.
Realizing Tae-sik has a soft spot for So-mi, Jong-seok kidnaps her and forces him to deliver the drug to Oh Myung-gyu. Man-seok informs the police, leading to them swarming Myung-gyu’s property. Myung-gyu escapes, while Tae-sik is arrested and discovers Hyo-jeong’s body, with her organs harvested, in the back of the car he used to make the delivery.
Tae-sik escapes from the police station, alarming them with his display of combat prowess. Upon further investigation, the police officers discover he was a former covert operator for the South Korean Army Intelligence, with numerous commendations, but he retired after he was wounded and his pregnant wife was murdered by a hitman.
Following the lead from the burner phone he received from Jong-seok, Tae-sik tracks Du-chi to a nightclub. As he asks where the brothers are, Ramrowan walks in and shoots at Tae-sik, killing Du-chi in the crossfire. The two fight to a standstill, and Tae-sik suffers a bullet wound. Bleeding out, Tae-sik finds his former partner, who performs an emergency surgery to remove the bullet. He recovers, asks his partner to help him acquire a gun, then goes back to the city.
Tae-sik finds and frees several child slaves in a drug manufacturing plant, in the process killing off the younger of the brothers, Jong-seok. He tracks down the elder brother, Man-seok, at the gang’s condo, where a dozen gang members and Ramrowan are also waiting. Man-seok says that he has had So-Mi killed and shows Tae-sik a container that has what he says are her eyes. He demands to know what happened to his younger brother, and, in a rage, Tae-sik kills the gang members, including Ramrowan and Man-seok.
As Tae-sik prepares to commit suicide out of grief, a scared and dirty, but unscathed So-mi emerges from the darkness; she had been saved by Ramrowan, who took pity on her because she had been kind to him – the eyes in the container belonged to the gangsters’ surgeon, who had been killed off-camera by Ramrowan. The police allow Tae-sik and So-mi to ride together after they arrest him, and, while she sleeps, Tae-sik asks if they can be dropped off at a small convenience store. Tae-sik buys a backpack along with other school supplies. He tells her that she’s going to be on her own now, as the police have to take him away.
Before he goes, he asks her for a hug and breaks down in tears as they embrace.