Originally an elite member of the Special Crime Unit in the Hong Kong Police Force, former cop Szeto Shun (Kevin Cheng) was forced to leave the force after getting implicated in an arson case. He is then hired at a security company, where he meets the intelligent Cheung Lik Hang (Ruco Chan).
With their similar ways of thinking and work styles, Shun and Hang become close friends. Their superior, Kong Wui Hoi (Lau Kong), also treats them as his left and right-hand men.
Shun encounters private investigator Jenny (Tavia Yeung), who triggers a memory he had long forgotten—new evidence in the arson case that had changed Shun’s life forever.