- 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. NIK-HANG's thoughts and tenor of his ways are similar to SHUN's, and he is also excellent at work. Gradually, the two become good friends.
Their supervisor KONG WUI-HOI (Lau Kong) also considers the two as his right-hand men until a private detective NG CHUN-NI (Tavia Yeung) appears. CHUN-NI mistakes SHUN for her old friend, triggering a dispute between the two. That makes SHUN reflect on the past event that he almost forgets about, which turns out to be involving the suspected arsonist. CHUN-NI, who is gifted with an eidetic memory, goes to probe into the matter together with SHUN and NIK-HANG. Unexpectedly, the closer they get to the full truth, the more intense the conflict between reason and law becomes. On top of that, the relationship among the three also undergoes a drastic change...