Kit, [Wu Jing], is a Hong Kong undercover cop who sinks into a drug habit to infiltrate a ruthless crime syndicate that kidnaps people and ships them to Thailand, where victims are killed for their organs on the black market. The mastermind behind the operation, Hung Mun-Gong [Louis Koo], carries a rare heart condition and needs a transplant to stay alive, with Hung’s younger brother standing out as the ideal donor. When Hung orders his men to kidnap that brother, a violent gunfight erupts after Kit tips off the police, and the chaos leaves Kit's world fractured: his allies are harmed, and the kidnapping operation is exposed.
Hung’s men manage to injure his brother, yet the police manage to pull him to safety, while Kit, now without a clean cover, escapes the kidnapping crew only to see his allies fall away. The consequences stretch far beyond the initial raid: Kit’s cover is blown, his friend is killed, and he is knocked unconscious before being dumped into a prison in Thailand. Inside the prison, a corrupt warden—Ko Chun—works for Hung and keeps kidnapped victims alive long enough to harvest their organs, turning the facility into a grim chamber of brutality.
In the prison, Kit fights to survive but is overpowered when he tries to escape, and his clashes with prison guards unfold in brutal bursts of force. Chatchai [Tony Jaa], the tough prison guard and a devoted father, becomes a central figure as his daughter Sa—who suffers from leukemia and needs a bone marrow transplant—awaits a donor. The donor who agrees to help Sa is Kit, tying Kit’s fate directly to Sa’s survival and heightening the stakes of every move he makes. Back in Hong Kong, Hung’s reach continues to press, and Hung reveals himself to Kit’s uncle and supervisor Wah [Simon Yam], who has been quietly watching Hung’s brother in hospital. Hung pressures Wah to hand over his brother in exchange for Kit, and Wah’s resolve wavers under the threat.
Wah shifts his stance, hiding Hung’s brother and assigning his own subordinates to guard him while tracking Kit’s location in Thailand. In a bid to seize control, Hung sends Ah-Zai, a dangerous knife-wielding assassin, to chase Wah’s team and to seize Hung’s brother. The pursuit escalates as Wah’s side advances, while in Thailand, Wah bribes Chatchai’s colleague Kwong [Ken Lo Wai-Kwong] to help locate Kit. Ko Chun soon captures Kit and Wah and orders Chatchai and Kwong to escort them to a remote hideout where victims are disposed of.
Once there, Kit and Wah break free and fight their way out, though the escape is costly: Chatchai and Kwong decide to turn and lend a hand, and the duo, battered but resolute, helps push toward safety. Chatchai is captured and tortured by Ko Chun’s men, intensifying the peril that surrounds all three men as they navigate a path through betrayals and shifting loyalties.
In a high-stakes confrontation, Hung’s brother is rushed to a medical center for the heart operation, and Kit infiltrates the facility to seize Hung and force Ko Chun to bring Chatchai to him. A brutal clash erupts as Ko Chun and his men close in, but Kit and Chatchai form a precarious alliance to fight their way free. Hung’s condition deteriorates during the chaos, and he dies after a final exchange that underscores the fragile grip on life held by all involved.
The climactic moment comes when Chatchai, in a desperate effort, saves Kit by preventing Ko Chun from wielding ultimate control. Kit clings to a chain as Ko Chun attempts to pull him into danger, and Chatchai stretches out his hand to pull Kit back to safety in a tense, decisive rescue. The film closes with Sa narrating that she received the transplant and remembering Chatchai’s embrace, while Kit watches from a distance, the weight of everything he endured lingering in the air.
