After cracking a major gang case, undercover agent Chen Fengxiang (played by Jordan Chan) was transferred to a civilian position for eight years and was recruited back by the anti-gang group. Since the most troublesome gang leader in the underworld is Chen Fengxiang's younger brother Zhang Zhiqiang, Chen returns to the "jianghu" and joins the anti-gang B1-1 team headed by Zhang Shaojun (played by Chen Guokun) to deal with the new villains, including former friends and enemies, which makes Chen in a dilemma. Fortunately, Chen and his teammates have developed mutual trust and tacit understanding during the cooperation. It is three years before Hong Kong's return to China, and the gang intends to take advantage of the situation to make a big move. When Chen was investigating the disappearance of a dragon head stick, he discovered a shocking conspiracy involving the century-old history of Hong Kong's underworld.