The films follows a series of encounters of a patrolling Police Tactical Unit of one single night, where the team tries to help an Organised Crime and Triad Bureau Sergeant Lo Sa to retrieve his lost revolver after he was assaulted by a group of triad members. The films portrays police officers' use of extralegal means to achieve investigative result and reveal the complex relationships between criminals and police officers, hostility among criminals themselves, and even rivalry among different bureaux within the Police Force.