The details of undercover police officers are deleted from a police database and a senior officer is left struggling to know who are the undercover officers and who are the criminals.

Nick Cheung Ka-Faias Blue
Louis Kooas Shiu Chi-Long
Francis Ng Chun-Yuas Q-Sir / Inspector Q
Charmaine Sheh Sze-Manas Ding Siu-Ka
Benz Hui Siu-Hungas Foon Hei-Gor
Moses Chan Hoas Police Superintendent
Louis Cheungas Triad Member
Clara Leeas Assassin
Li Guangjieas Tung Pak-Ho
Zhang Huiwenas Siu Ying, Blue's Bodyguard
Kenny Tse