Walk on Fire

During Tong Heung-tung's return to Hong Kong from Macau, the Hunan Gang ambushes the police van. Tong escapes with their help, and the operation sows chaos in the repatriation process. The incident triggers a new cycle of pursuit between the police and the gang.

Lee pursues the Hunan Gang across the border and captures their members. The operation leaves behind destruction that angers his superior Chan. The arrest marks a dramatic escalation in the pursuit of Wai's gang.

Wai's gang drags Lee to the pier, brutalizing him and forcing him into drink. They make him drive himself into the ocean, killing him in the process. The death is the catalyst for the ensuing investigation and vengeance.

The next morning, May gives birth to Lee's baby boy. She is saddened by the news of her husband's death, setting a somber tone after the tragedy. The family begins to grieve while the case remains unsolved.

Lau and Lo Mo decide to take up the investigation themselves. They locate Chung after she crashes out of a nightclub and is harassed by narcotics officers. Lau rescues her and brings her to a restaurant, but Chung escapes and heads toward her grandmother's house as the gang closes in.

The gang tracks Chung to her grandmother's house and attempts to burn it down to silence her. Lau and Lo Mo rush to rescue Chung and her grandmother from the blaze. They manage to save them and press on with the case.

Chung tells Chan that Wai and his gang were involved in Lee's disappearance, but Chan refuses to believe her. The lack of trust deepens the rift between the investigators and the official line. Lau grows more determined to pursue the truth.

Angered by inaction, Lau takes the case into his own hands and lets Chung stay with him. He recruits a lowlife Triad, Al, to help coax Squid Chiu into cooperating by masking his involvement with Lau's apparent influence. Al initially resists but is won over by Lau's pressure.

Lau and Al set up a ruse to get Chiu to cooperate by posing Lau as the son of a jewelry-store owner and asking Chiu to rob the store. Chiu arrives and agrees to consider the plan after being pressed, for fear of crossing Lau. Al ends up helping to stage the deception.

Lau asks Lo Mo to arrange using his future father-in-law's jewelry store as the target. Chung is meant to accompany Lo Mo's father-in-law to attract Chiu's attention. The setup relies on Chung's involvement and the promise of a payoff.

Chung carries heroin-laced cigarettes that Lau discovers and discards to keep the plan on track. A traffic jam en route to the store adds pressure, and Chung's withdrawal temptations surface. Lo Mo arranges methadone to stabilize her for the operation.

The team executes the airport robbery plan by kidnapping the Taiwanese drug dealer and fleeing in a van while being pursued by police. Lau's disguise helps them slip away with the money. Interpol activities and suspicion swirl around the operation as authorities pursue leads.

At Interpol Headquarters, an undercover agent is described as overweight, leading to misidentification of the police crew. Lo Mo attempts to misdirect investigators but is questioned before being released. The fake lead buys time for the plan to unfold.

Wai leads the Hunan Gang into the jewelry store, triggering a brutal chase and rooftop gunfight. Chung is fatally wounded during the chaos, and Lau shoots Wai to stop him. The intensity of the shootout ends only with Wai's death and Chung's, devastating Lau.

Chung dies in Lau's arms after expressing she never felt cared for. In the aftermath, Lau and Lo Mo are arrested for robbing Chan Kwok-chiu at the airport, ending their vigilante mission. The case closes with the cost of vengeance weighing heavily on them.