Seven years ago , he went undercover and became the undercover protege to Hung Kai - pang ( Jiang Wu ) , a wanted criminal specializing in bombs .
Cheung Choi - san ( Andy Lau ) is a superintendent of the Explosive Ordnance Disposal Bureau ( EOD ) .
Seven years ago , Cheung Choi - san went undercover and became the undercover protege to Hung Kai - pang ( Jiang Wu ) , a wanted criminal specializing in bombs .
Cheung Choi - san ( Andy Lau ) is a superintendent of the Explosive Ordnance Disposal Bureau ( EOD ) .