Former CTRU partners reunite after a murder, tensions arise. Leader Fong recruits Kiu, igniting rivalry between To, attracted to Kan, and Kiu who enlists criminal Hong's aid after explosions, despite Hong's hidden agenda.

Kan Yiu-yeung (Kenneth Ma), Ku Ka-keung (Joel Chan), Kiu Po-po (Natalie Tong) and Kiu Tai-nam (Jazz Lam) were once CTRU's Formidable Quartet. An incorrect decision in an operation caused the breakup of their friendship. And the quartet went their separate ways. Fast-forward to the present and an indiscriminate homicide again brings the quartet together. But there are still certain unresolved issues between themselves. POTT is Counter Terrorism Intelligence Cadre's other elite task force. Team leader Fong Kwok-hei (Elena Kong) admires Po-po and asks her to become her subordinate. Team member To Siu-jie (Moon Lau) fancies her partner Yiu-yeung and finds out Po-po is Yiu-yeung's ex-lover, so she "starts a war". Successive explosions happen in the city. While investigating, Po-po asks prisoner-cum-hard criminal Dr. Hong's (Ruco Chan) for help, and the process is surprisingly easy. Actually, Dr. Hong has some trick up his sleeve.