Officer Cheung (Andy Lau) is the most respected member of the Explosive Ordnance Disposal (EOD) unit. Before rising through the ranks, Cheung worked undercover within a criminal gang, led by a ruthless crime boss notorious for his expertise in explosives. After Cheung’s undercover work leads to the breakup of the gang and the arrest of the boss’s brother, the gang boss swears to take revenge on the man responsible for ruining him. Explosive attacks begin breaking out across the city, escalating until a shocking hostage situation unfolds within one of the world’s busiest tunnels. With the city facing what seems to be an impossible to stop threat, it is only Cheung who has the skills needed to end the crime boss’s revenge spree.