Detectives Chung and Li suspect their superior, Siu To, of colluding with triads. Li discovers that his girlfriend was assaulted by a john associated with Siu To and seeks revenge. Later, when Siu To is implicated in a rape case, their subordinate, Ma, obtains evidence but is murdered, and witnesses are intimidated to leave the city. Chung is committed to making a big prosecution in the name of justice.