While undercover officer Kit is taken prisoner by the syndicate, he befriends his keeper and discovers an organ trafficking ring.
Hong Kong police officer Kit (Wu Jing) goes undercover in order to catch Mr. Hung (Louis Koo), the mastermind behind a crime syndicate. When the operation goes sour, and the undercover cops are betrayed, Kit disappears without a trace. Uncle Wah (Simon Yam) defies the order from his commanding officer and tracks Kit to a prison in Thailand. Thai Police officer Chai (Tony Jaa) becomes a prison guard in order to raise money for his daughter who has leukemia. He's assigned to keep an eye on Kit. Even though Chai and Kit are in opposing positions and they don't speak a common language, Kit turns out to be a suitable bone marrow donor who can save Chai's daughter. While Chai is determined to keep Kit alive, the warden Ko (Zhang Jin) wants him dead to ensure the smooth operation of the prison, which is the front for Mr Hung's organ trafficking business. Mr Hung shows up in Thailand so he can use his younger brother's (Jun Kung) heart in a heart transplant to save his own life. The stage is set for a showdown...—Jalan Harris
After busting a local gangster Hong in an undercover operation, hard-boiled cop Kit is captured by Hong's men and wakes up in jail in Thailand facing a life sentence. While in police custody, Hong strikes a deal with Kit's supervisor Wah to trade his freedom for Kit's. Wah traces Kit to Thailand and manages to convince to new prison guard Chai to help save Kit because Kit is one of the few eligible bone marrow donors who can save Chai's daughter, who's suffering from leukemia. Hong breaks out of jail and flees to Thailand and order Kit's executive. When Kit learns of Hong's jailbreak, he's determined to bring him to justice.
