Sergeant Tong is wracked with guilt after he unwittingly kills a young girl whilst capuring a criminal named Cheung. When the girl's sister is later kidnapped in a ploy to get Cheung released, Sergeant Tong vows to find and rescue her before she comes to harm.
A police detective must solve a brutal murder to prove his partner's innocence and unearth the truth behind Hong Kong's police force. The investigation brings him to an unlikely collaboration with an inspector from the Narcotics Bureau, whose motives may not be what they seem.
Ho Sau, an undercover agent, has been working with Yau, a drug lord, for years, but his job and family are in trouble.
