Lam Wai-tung, [Michael Miu Kiu-Wai], is dying from cancer and hatches a desperate plan to steal a batch of diamonds from smuggler Chiu Ying-kau, [Dick Wei], to fund his younger brother Wai-leung's medical studies overseas. Wai-leung himself is blissfully unaware of his brother’s illicit activities, trusting that family loyalty will see him through. After the heist, Chiu is questioned at the police station by Kwat, [Chan Chik-Wai], and Sergeant Ben Kwok, [Aaron Kwok], who suspect a link to the case but lack solid evidence to convict. The tension tightens as Wai-leung, Ben, and Ben’s sister Man, [Charine Chan Ka-Ling], throw a surprise birthday party for Wai-tung, a moment that momentarily softens the grim reality surrounding their hidden danger.
Wai-tung leaves the party early to negotiate a ransom with Chiu, but he has secretly swapped the real diamonds for counterfeit ones. The arrangement collapses when Chiu warns Wai-leung by hinting at Wai-leung’s own involvement, forcing Wai-tung to rush back to warn his brother. En route, Wai-tung is ambushed by Chiu’s henchmen and stabbed to death, the counterfeit diamonds slipping away to the shadows as the killers vanish. Ben catches a glimpse of one face among the fleeing men, a clue that deepens the investigation. At the station, Ben learns the mysterious figure is known as Big Head, a name associated with a powerful insider linked to Chiu, while Kwat explains that Chiu operates high up in the criminal network. Ben shares his growing suspicions with Wai-leung, who refuses to believe his brother could be implicated, setting up a volatile rift between them.
Wai-leung then becomes a target himself: a phone call from Chiu warns him that the diamonds are fake and threatens his life unless he can procure the real ones. Desperate to trap the smugglers, Wai-leung agrees to play along, calling the police from outside while secretly guiding the smugglers toward a trap at his apartment. But Man’s arrival disrupts the plan, forcing Wai-leung to retreat and he is captured by Chiu’s men. The torture is brutal, and Wai-leung collapses from his wounds as Big Head—an alias mentioned by the police—falls to a separate firing squad of henchmen. Yok, another of Chiu’s lieutenants, shoots Big Head to prevent a tighter police net and plants the body to mislead investigators. Wai-leung is then framed for murder, fleeing into a cruel twist of fate that ends with him being struck by a passing car driven by Migo, a Japan-based reporter played by Yukari Ôshima.
Miko’s presence complicates matters further: she forces Wai-leung to his old home to hide and recover while she uncovers his personal diary, revealing the painful truth of his cancer diagnosis and the motive behind his alliance with Chiu. Back at the murder scene, Ben and Kwat press on, doubting the eyewitness who pointed to Wai-leung as the killer of Big Head, and they begin tailing Chiu, bugging his car, and hiding in the trunk to gather hard evidence. They discover that Miko is an informant hired by Ben to monitor Wai-leung and learn the diamonds’ location, adding another layer of betrayal and risk to the investigation. When Miko returns to Wai-tung’s house, she finds Wai-leung missing and leaves behind a voice recording detailing his plan for revenge against Chiu.
As the pursuit tightens, Wai-leung openly shoots at Chiu, threatening to escalate into all-out violence. Ben restrains him to prevent a reckless bloodbath, and the trio—Ben, Wai-leung, and Man—reunite in a tense stalemate, still lacking decisive evidence to arrest Chiu. Miko arrives, and Ben immediately recognizes her, accusing her of working for Chiu, though Wai-leung defends her. A chaotic confrontation ensues when Miko, cornered, fights alongside Wai-leung and Man; a struggle spills over the room, and diamonds tumble free as a table is knocked over. Miko seizes Ben’s gun and handcuffs Wai-leung and Ben to a metal beam, hinting at a shifting allegiance. However, a change of heart prompts her to try to aid Wai-leung, returning Ben’s gun to Man through the chimney before rushing back to confront Chiu. In the ensuing melee, Wai-leung uses Ben’s weapon to free them, and Miko resumes her stance against Chiu, holding him at gunpoint long enough for the diamonds to be returned to him in exchange for Wai-leung and Ben’s safety. But Yok ambushes her, and the pivotal battle that follows sees them fighting off Chiu’s henchmen, sustaining serious injuries in the process. In a final act of controlled fury, Wai-leung wounds Chiu with a knife in their fateful struggle, but Ben attempts to de-escalate. The moment seems poised on a knife-edge until Chiu makes a last, brutal attempt to blindsight them, prompting Wai-leung to shoot Chiu to death in a quiet—yet decisive—end to the case, leaving the trio battered but resolute.
In the aftermath, the threads of loyalty, family, and justice intertwine as each character confronts the consequences of desire, deception, and danger. The film unfolds as a layered crime drama where trust is scarce, motives are murky, and every truth comes at a price, with each actor’s turn contributing to a mood of gritty persistence and slow-burn revelation.
