Kan Yiu-yeung, Ku Ka-keung, Kiu Po-po and Kiu Tai-nam 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 admires Po-po and asks her to become her subordinate. Team member To Siu-jie 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 for help, and the process is surprisingly easy. Actually, Dr. Hong has some trick up his sleeve.
Beaten down by the gangster for the last time, Parking attendant Chan Yiu-Hing opens a security business and becomes an underworld hero himself. When his girlfriend wants to settle down, Chan realizes he can't outrun his past.
Former friends Kwok Pak-fei, Keung Hei-man, and Lau Lik reunite years after a botched operation led to a tragic death and estrangement. Now, a gruesome murder case tied to a human trafficking ring forces them to work together. As they investigate, mysterious messages appear with clues about the crimes, hinting at knowledge from the future. Together, they form a special unit, ASIB, to decode these messages and solve the chilling case.
