A story that tackles the life experience and mental issues that plague the PTU officers from the perspective of a former undercover cop who returns to the force.After successfully bringing down the triads, Gao Jiasheng (Raymond Lam) goes back to wearing the police badge and crosses paths with Sergeant He Huiling (Charlene Choi) and Team Leader Liu Jianhui (Alex Fong). The three have their share of misgivings, but learn to build trust and friendship through a series of dangerous missions.