On a rainy night in Shenzhen, a female prostitute named Sze-kam Oi-yee is strangled by female wanted criminal Yip Siu-ngan who aims to assume her identity. Ngan passes customs and quietly slips into Hong Kong, and after reporting the loss of her own ID card, she successfully obtains Yee’s identity. Yee has a Hong Kong ID because her husband is a Hong Kong resident, who was waiting for his wife's arrival.
Siu-ngan then crosses into the complex world of the city’s underbelly, where she meets Chan Kai-ming, a taxi driver who is divorced and has left his daughter Yin Yin in the care of his mother, a detail that underscores the delicate web of loyalties she plans to exploit. Ngan fixes on Ming as her next target and first runs him over with a car to cripple him, then sneaks into his house to hold him hostage and probe into his life. One night, Ming's mother comes to visit, and the ruthless Ngan kills her so she won’t blow her cover, further enabling her scheme to defraud Yin.
On the day Ngan receives her real Hong Kong ID card, Yee's husband finds Ngan suspicious and shadowing her to Ming's house. While he confronts Ngan, her husband, Kwan Fai, arrives and kills him. The two criminals, now bound by fear and shared culpability, press on. Fai, crippled in both hands, intends to steal Ming's identity—and even his arms—to solidify his deception. In a brutal moment, Fai chops off Ming's arms and attaches them to himself, successfully taking Ming's identity.
Just as the plan seems to reach a chilling culmination, Yin escapes from the couple and is later found by construction workers, exposing the fragility of the criminals’ facade. The truth comes to light, and Ngan and Fai find themselves hunted once more by the Hong Kong police, forcing them to hit the road in a desperate bid to outrun justice. Setting out on that fugitive path, Ngan speaks to Fai with stark resolve: > blame the moment that I was softhearted, I was not cruel enough before, but it does not matter, I will do better next time.
