Zhang Zaishan (played by Andy Lau) is a senior inspector of the "Explosive Ordnance Disposal Division" of the Hong Kong Police Force. Seven years ago, he lurked in the criminal gang of the most wanted criminal Huobao (played by Jiang Wu). During a robbery of the vault, Zhang Zaishan revealed his identity as an undercover bomb disposal team member, and cooperated with the police to successfully prevent the bomb from detonating, and wiped out the criminal organization of Huobao and his brother. Unfortunately, Huobao escaped at the critical moment and vowed to take revenge. After reinstating, Zhang Zaishan was quickly promoted to a bomb disposal expert in the police force. Seven years later, Hong Kong suffered a series of bomb terrorist attacks. The police received a tip-off that a large number of explosives had been smuggled into Hong Kong. All signs showed that a major case would occur in Hong Kong. Just as the people of Hong Kong were in panic, the busiest Hung Hom Cross-Harbour Tunnel in the city was blocked and intercepted by gangsters, and hundreds of hostages were held hostage. Huobao, who finally appeared, threatened the police to blow up the tunnel. Zhang Zaishan could only bring Huobao to justice to dismantle the shocking conspiracy behind this anti-terrorism storm.