Hong Kong thriller in which bomb disposal expert Cheung Choi-san (Andy Lau) is in a race against time to prevent a terrorist from blowing up an underground water tunnel which could have catastrophic consequences for the citizens of Hong Kong. After becoming an undercover associate of wanted gangster Hung Kai-pang (Wu Jiang), Cheung learns of Hung's criminal enterprise and his penchant for using explosives. When a covert operation results in Hung's escape and the capture of his gang and younger brother, he later returns to have his revenge and threatens to blow up the underwater tunnel with hostages in tow. Can Cheung diffuse the situation in time before many lives are destroyed?