Cheuk Hoi (Michael Miu) is a Chief inspector of Hong Kong's Criminal Intelligence Bureau (CIB) police unit. He is a righteous supervisor that will resort to unethical tactics in order to restore the identities of his undercover subordinates who have gone missing and deemed by the police department to have strayed to the criminal side. When he finds his friend Hong To Hang, a fellow Chief inspector in the CIB unit, thrown off a building under mysterious circumstances, he learns from Hong's dying words that there are moles within the police force working for the triads. In order to protect the lives of his five undercover agents, Hong has deleted their files from the police database, erasing their identities as police officers. Hong charges Hoi with the task of finding each lost undercover agent, but dies before he can tell Hoi any further information. Remembering Hong's warning against trusting anyone in the police force, Hoi keeps Hong's last words hidden from his superiors. Instead, ...