Former regional crime unit officer SZETO SHUN (Kevin Cheng), who is suspected in connection to an alleged arson, has to resign from the police force and change his career to join a security company, where he encounters CHENG NIK-HANG (Ruco Chan). Although SHUN, the former elite cop, seems a bit aloof, he is very observant, and often recognizes rarely-known clues from surveillance videos to help solve criminal cases.