As a Senior Inspector of the Narcotics Bureau Operation Unit, HEUNG WING (Miu Kiu Wai) profoundly abhors evil. He and WAI SAI-LOK (Raymond Lam) – Senior Inspector of the Intelligence Unit have closely co-operated with each other as peer mentors, frequently solving drug trafficking cases for the Police Force. During an operation to knock down the targets, SAI-LOK discovers clues that HEUNG WING is most likely the corrupt cop in a collusion conspiracy with drug dealers. Apart from launching a secret investigation into HEUNG WING, SAI-LOK is also alienated from him by the evil-willed Chief Inspector of the Operation Unit – PUN HOK-LAI (Ben Wong). Having undergone various disputes against each other, the long-term brotherly relationship between SAI-LOK and HEUNG WING appears full of contradictions.
On the other hand, following an investigation, SAI-LOK falls in love with a snitch – CHAN KA-PIK (Kate Tsui), who suffers from low self-esteem due to her humble beginning. Deliberately denying her affection to SAI-LOK, KA-PIK gives up on him so that his secret admirer – KO HEI-SUEN (Ella Koon), a rookie police officer, can have the chance, leading to a subtle relationship among the three. Feeling life is so dreary, KA-PIK ultimately digs her own grave by becoming a new generation of drug dealer, involved in drug trafficking and provoking the Police Force. With intense sorrow, SAI-LOK then joins forces with HEUNG WING against KA-PIK, waging a chain of bitter battles.