While he was tailing a Jockey Club trader in his investigation, Principal Investigator William Luk (Louis Koo) of the ICAC witnessed the murder of the trader by a lone assassin (Chou Yu Min).Inspector Lau Po Keung (Julian Cheung) of the Crime Unit was assigned to the murder and got nowhere with Luk's testimony as Luk refused to disclose anything pertaining to his own investigation.Another classic run-in between the Police and ICAC was in the making.When the Police investigation led to someone called Teacher (Lo Hoi Pang), the biggest player who controls the illegal bookmaking on football betting in Hong Kong, Terry Lun (Bowie Lam), the Security Manager of the Jockey Club was murdered. While Lau was in hot pursuit of the assassin, the assassin escaped with the help of Lau's sister, Ebby (Dada Chan).The hired hit was ordered by Big Boss, the mastermind behind an international crime syndicate who manipulated football matches in Europe. His partner was Ha Chi Yin (Shek Sau), one of the directors of the Jockey Club who was the shoo-in candidate as the next Chairman.Two disciplined forces embarked on the case with mutual distrust ended up with rapport and understanding to uproot the crime syndicate...