→Plot: minor changes
Kit is a Hong Kong undercover cop who becomes a drug addict to infiltrate a crime syndicate which has been kidnapping people and sending them to Thailand, where
they are killed and have their organs sold in the black market. The mastermind behind the syndicate, Mr Hung, has a rare heart condition and needs to undergo a heart transplant to prolong his life. Hung's younger brother is the ideal donor for a heart but he is unwilling to.
When Hung sends his goons to kidnap his brother, the situation goes haywire and a gunfight breaks out because the police has been tipped off by Kit about the kidnappers' plan. Hung's brother is injured during the shootout but is rescued by the police. Kit, on the other hand, escapes with the kidnappers but his cover
has already been blown. Hung's men knock him unconscious and send him to a prison in Thailand. The chief warden, Ko Chun, works for Hung and has been keeping the kidnapped victims alive in the prison before they are killed for their organs. Kit is made to serve a life sentence in the prison.
While in prison, Kit
relentlessly tries to escape and fights with the prison guard Chatchai on a few occasions but ends up being subdued every time. Chatchai's daughter has [[leukaemia]] and needs a [[bone marrow]] donation to survive. Chatchai witnesses Ko Chun's illegal activities and brutality but forces himself to remain quiet because he does not want to lose his job. Ironically, the donor who agreed to donate bone marrow to Chatchai's daughter is actually Kit.
Back in Hong Kong, Hung reveals himself to Kit's uncle and supervisor, Wah, who is keeping a close watch on Hung's brother in hospital. Hung threatens Wah to hand over his brother to him in exchange for Kit. Although Wah initially agrees
to hand over Hung's brother, he changes his mind later and hides Hung's brother in his friend's house. He then leaves his subordinates behind to guard Hung's brother while he tracks down Kit's location in Thailand and travels there.
In Thailand, Wah
manages to bribe Kwong, Chatchai's colleague, and enter the prison to find Kit. Shortly after Kit and Wah are reunited, they are discovered by Ko Chun, who captures them and orders Chatchai and Kwong to escort them to the hideout where victims are killed and have their organs removed. At the hideout, Kit and Wah break free from captivity and fight their way out. On the other hand, Chatchai and Kwong have a change of heart and turn back to help Kit and Wah. Kit, Wah and Kwong manage to escape despite sustaining very serious injuries; Chatchai is captured by Ko Chun's men, who tie him up and torture him.
In the meantime, back in Hong Kong, Hung's knife-wielding henchman Ah-zai kills Wah's colleagues
and other police officers, kidnaps Hung's brother and brings him to a medical centre in Thailand for the heart operation. However, Kit breaks into the centre, defeats Ah-zai, and takes Hung hostage. He then demands that Ko Chun bring Chatchai to the centre in exchange for Hung. A fight breaks out when Ko Chun shows up with his men and Chatchai. Kit and Chatchai team up and manage to defeat all of Ko Chun's men. At the same time, Hung breaks free from his restraints and beats up his brother, but his medical condition also deteriorates and he becomes blind as a consequence.
Kit and Chatchai are seemingly no match for Ko Chun after engaging him in a long fight. At one point, Chatchai is knocked out after being stabbed by Ko Chun, who then proceeds to pound Kit against the window until the glass shatters. While in his unconscious state, Chatchai
experiences a vision of his daughter in danger and immediately gets up and knocks Ko Chun out of the window. However, when he realises Kit has also fallen out of the window, he throws out a chain to Kit for him to hold on to, but Ko Chun grabs the chain instead. Kit then grabs on to Ko Chun's tie and eventually strangles him to death ; Chatchai stretches out his hand and pulls Kit back to safety. The movie ends with Chatchai hugging his daughter while Kit watches from a distance away.