A love story between Yang Kang-Cheol (Jung Woo-Sung) - an ex-prisoner who was incarcerated because of his friend's conspiracy - and a sensitive, yet guarded veterinarian, Jung Ji-Na (Han Ji-Min). They meet by chance and begin to fall in love with each other ...
Kang-Cheol and Gook-Soo (Kim Beom) leave prison on a furlough. Kang-Cheol has been in prison for 16 years. They have only one month left until their release. They are both given cellphones to take with them. When the phone rings they have to immediately answer where they are and what time it is. Both men are extremely excited to be on the outside. They get on a crowded subway and are pushed by other passengers. Kang-Cheol ends up in front of a woman. The woman's name is Ji-Na (Han Ji-Min) and she asks Kang-Cheol to give her some more space. Kang-Cheol can't move, though. When Ji-Na gets off the subway train she kicks Kang-Cheol and flips him the bird as the train departs. After Kang-Cheol and Gook-Soo get off the train they board a public transit bus. Gook-Soo asks Kang-Cheol to come and stay at his dad's house. Kang-Cheol doesn't like the idea and wants to meet a friend that was released from prison. Kang-Cheol saved his friend's life twice while in prison.
Kang-Cheol got off the bus without Gook-Soo knowing. Kang-Cheol then goes to a motel and has a good time alone. He then goes out to meet his friend from prison. On his way he spots a woman who looks familiar. Kang-Cheol then realizes the woman is the lady from the subway who kicked him. She is arguing with another man on the street. The man is holding a small dog and Ji-Na is insisting that the dog doesn't belong to him. The man then bumps into Kang-Cheol who is waiting for a taxi cab. When Kang-Cheol yells at the man, Ji-Na suddenly grabs the dog and runs. Kang-Cheol then spots a man in black suit who seems to be following him. Kang-Cheol thinks back and remembers the guy. The man is someone who falsely accused of Kang-Cheol of beating him. Kang-Cheol runs after the guy in the black suit, but loses him. Instead, Kang-Cheol bumps into Ji-Na who is still hiding from the dog-napper. They hide until he goes away. Ji-Na leaves with the dog and Kang-Cheol goes to meet his friend at bar.
When Kang-Cheol arrives he overhears his friend from prison talk about Kang-Cheol in a disparaging manner. The man states that he doesn't even want to meet Kang-Cheol, but that he has no choice. Kang-Cheol becomes enrage and goes out to smash his friend's car. The man begs Kang-Cheol for forgiveness.
The next day, Kang-Cheol learns that his ex-girlfriend died. Kang-Cheol goes to a temple where her ashes lay. There, Kang-Cheol meets the friend of his ex-girlfriend. The woman tells Kang-Cheol that he has son. His ex-girlfriend gave birth to the boy and raised him by herself. Kang-Cheol doesn't believe her. Kang-Cheol had a relationship with her friend when he was 17-years-old and they had sex only one time. Nevertheless, the woman insists the boy is his son. The teenage boy stands not far from them and watches. The woman tells Kang-Cheol that he should take the boy. Kang-Cheol refuses and leaves. While Kang-Cheol is walking away the boy comes up to Kang-Cheol and spits on his face. Shortly later, while Kang-Cheol is crossing the street, he is hit by a car. The driver gets out of the car and the person turns out to be Ji-Na. Kang-Cheol is taken to the hospital while Ji-Na goes to the police station. When Kang-Cheol wakes up he decides to leave the hospital. Out on the street he receives a phone call, but it's not from prison. The phone call is from Kim Chan-Gul (Kim Jun-Seong). When they were in high school Kim Chan-Gul stabbed another boy, who just happens to have been Ji-Na's uncle. Kang-Cheol was framed by Kim Chan-Gul and went to prison for 10 years for the stabbing. When Kang-Cheol was released from prison for the stabbing, Kim Chan-Gul then got the guy in the black suite to accuse Kang-Cheol of assaulting him. Kim Chan-Gul is now a prosecutor and his father is about to be become a justice for the Supreme Court. Kim Chan-Gul warns Kang-Cheol over the phone to live a quiet life. The phone then suddenly stops working.
Meanwhile, Kang-Cheol's prison officer Kim becomes worried as Kang-Cheol did not answer his cellphone. His parole officer tried to call him while he was unconscious in the hospital. Prison officer Kim calls Gook-Soo looking for Kang-Cheol. The next day, when they are supposed to return to prison, Gook-Soo finds Kang-Cheol sleeping on a bench and they are both able to get back to prison in time.
Back in prison, a prisoner named Jin-Goo tries to provoke Kang-Cheol by attacking Kang-Cheol's friend. Gook-Soo tries to calm Kang-Cheol down. During excercise time though, Jin-Goo again attacks Kang-Cheol's friend. Kang-Cheol can't take it anymore and attacks Jin-Goo. Prison officer Kim runs toward them while yelling at them to stop. While trying to break up the fight, the prison officer is punched with a vicious left hook by Kang-Cheol. The next moment, prison officer Kim is laying on the ground, blood streaming from his skull onto the yard to form a disturbingly large pool of reddish mud. Prison officer Kim dies. Kang-Cheol is then sentenced to death by hanging. Right before he is to be hanged, Kang-Cheol thinks back to his past. He thinks of his mother who ignored his phone call and when he was hit by the car driven by Ji-Na. He isn't sure if he is already dead or not.
