Sergeant Ko Fai (Ruco Chan) completed undercover operations many years ago, and there is always a cloud hanging over him. Ko Fai is reassigned to a police precinct that is Crime Squad Station Sergeant Fong Chi-kiu's (Alice Chan) territory. While investigating cases, the duo gradually familiarize with each other and develop some tacit understanding. Chi-kiu is so dedicated to her job that she has no time for taking care of her family. Her son even hangs out with the wrong crowd and gets into trouble. Hotpot restaurant lady boss Lo Sin-man (Sharon Chan) was naive when she was young as she slept with gang boss Law Wai (Joseph Lee) and gave birth to a girl called Lo Siu-po (Kaman Kong). Fortunately, Ko Fai has always taken care of Sin-man and her daughter. Siu-po becomes a KOL and wants to step into the spotlight by engaging in reckless maneuvers. She gradually descends into the abyss as she reveals how drug dealers go about their business. To protect their loved ones, Ko Fai and Chi-kiu become guardians of the night and are determined to eradicate the villains.
