Plot: Set in Hong Kong, China, four years after the events in Line Walker, Sit Ka-keung (Raymond Lam) continues to work as a Hong Kong Police Criminal Intelligence Bureau (CIB) undercover officer, while Cheuk Hoi (Michael Miu) opens a coffee shop after being released from prison. CIB Chief Inspector Cheung Kei-gee (Mandy Wong) suspects Check Hoi of joining the triad and investigates him