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 the victims 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.
When Hung sends his men 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 is 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 attempts to escape twice and fights with the prison guard Chatchai but ends up being subdued every time. Chatchai's daughter has [[leukaemia]] and needs to undergo a [[Hematopoietic stem cell transplantation|bone marrow transplant]] 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.