My only disappointment is that the film isn't available on Blu-Ray.
Storyline - Warning, contains spoilers.
Kim Sun-woo (Lee Byung-hun) is an enforcer and manager for a hotel owned by a cold, calculating crime boss, Kang (Kim Yeong-cheol), to whom he is unquestionably loyal. The two share concerns over business tensions with Baek Jr., a son from a rival family, which is when Kang assigns Sun-Woo what is perceived (at first) to be a simple errand while he is away on a business trip to shadow his young mistress, Heesoo (Shin Min-a), for fear that she may be cheating on him with another, much younger man, with the mandate that he must kill them both if he discovers their affair. As he performs his duty following Heesoo, and escorting her to a music recital one day he becomes quietly enthralled by the girl's beauty and innocence, as glimpses into his lonely, empty personal life become more prevalent.
When he does come to discover Heesoo's secret lover directly in her home, he fiercely beats him, but seeing the girl's traumatized state causes him to take pause, pulled by his attraction to her. He thus spares the two on the condition that they no longer see each other again, causing her to harbour enmity towards him, despite the fact he had saved their lives at his own expense.
Meanwhile, Sun-woo continues to be embroiled in personal business with Baek Jr., over having beaten up several of his henchmen earlier for overstaying their welcome at the hotel. He is then threatened by one of his enforcers to apologize, but he adamantly refuses, fueled by his frustrations over Heesoo. As he relaxes in his apartment later one night, he is suddenly kidnapped by Baek's men to be tortured, but before they can do so, they receive new orders via phone call, and he is abruptly carried off to Kang, who has returned from overseas and has found out about his attempted cover-up of Heesoo's affair. Kang's men torture him into confessing why he lied, until he is left alone to think about his answer. A daring but messy escape follows, after which Sun-woo plans his revenge.
Help from one of Sun-woo's loyal co-workers provides him with money and new clothes to go about his plan: he secretly delivers Heesoo a gift to make amends, and he sets up a meeting with some local arms dealers, but as they work for Kang's organization, he ends up killing them over a deal to buy a handgun this incurs a vendetta with the brother of one of the dealers, who promptly sets out to find Sun-woo. He then goes on to set up a fake rendezvous with Baek Jr., exchanging words and killing him as well, though he is viciously stabbed in the process. Bleeding, his violent shooting spree leads directly to Kang amidst one of his business meetings, where he vents at him his anger over how badly he has been treated, despite his many years of service. Kang remains coldly indifferent to his plight, seeing his position as absolute in the matter. Sun-woo then shoots him, prompting a shootout with Baek Jr.'s henchmen, who had quickly picked up his trail.
Sun-Woo emerges as the only survivor of the battle, with the arms dealer's brother finally catching up to him in the same room. Now dying from multiple gunshot wounds, he pauses to reminisce on his only day with Heesoo, when he had escorted her to her music recital; in his memory, as he watches her play her cello, he finds himself overwhelmed with emotion and, in a rare moment of contentment for Sun-woo, he smiles. As he sheds a tear over this memory, the brother puts a bullet in his head.
The next scene shows Sun-Woo looking out of a window at the city below him and then beginning to shadowbox his reflection in the glass. The ending is left ambiguous, as the viewer is unsure if everything that happened was a dream or if it is only a flashback.
(Reference - www.imdb.com)