Prison on Fire

Lo Ka-yiu is convicted of manslaughter for accidentally pushing a robber into the street and under a passing bus, and is sentenced to three years in a Hong Kong prison. He begins serving his sentence and adjusts to life behind bars.

Early in his sentence, Yiu befriends Chung Tin-ching while working in the prison, and the two men form a cautious alliance amid the harsh environment. They support each other as they navigate prison politics.

Yiu watches a member of boss Micky's triad steal scissors from Ching in the laundry. He tells Ching, who retrieves the tools, but the incident earns him the triad's enmity and puts Yiu in danger.

During a cell search, several inmates are questioned by ranking warden Hung after prohibited items are found. Hung tries to recruit Yiu as an informant, but Yiu rejects. To resolve the matter, Hung agrees to transfer one of Micky's rivals to another prison, moving several triad members as punishment.

The next night Yiu is dragged into the lavatory and beaten by Micky's henchmen while Ching tries to intervene. A guard arrives and Yiu says he slipped, but the damage is done.

Yiu's girlfriend visits him and reveals she will study in England for nine months. He cannot persuade her to stay, signaling the strain between his prison life and personal life.

Micky pressures Yiu for compensation; Yiu publicly accuses him of calumny, sparking a brawl. Yiu fends off opponents with a shard of glass, but Ching is accidentally injured in the melee.

Yiu and Ching are summoned by the warden, and Ching accuses Hung of manipulation. The warden promises an investigation, and both men are temporarily placed in solitary confinement.

On New Year's Eve, Ching explains why he's imprisoned: years earlier he caught his wife prostituting herself and killed her in a misguided act, then faced murder charges. Their son visits him in prison.

In the following summer, Micky is transferred back into the prison and still seeks revenge. Yiu asks Officer Hung to move him and Ching to a different prison, but Hung refuses.

During a prison inspection, Hung denies the presence of triads among the prisoners. The warden requests a report, while Yiu and Ching are left to cope with the situation, unable to secure a safer move.

Bill's triad initiates a hunger strike to protest cigarette prices; Micky's men join. Hung pressures the group, defaming Yiu as the instigator, and secretly hints to Ching that he would rat them out. The warden orders everyone to resume eating, escalating tensions.

A massive fight erupts when the guards are absent and Micky's men attack Yiu and Ching. Ching defeats Micky, nearly killing him with a bed pole, and Hung is knocked down by a drop-kick; Ching bites Hung's ear in the chaos.

A few months after the climactic clash, Yiu is released and greeted by his family. As they leave the prison, they see Ching being moved back to the prison by bus after his hospital stay.