Young Hong Kong police officer Ho Ka-Po (Kate Tsui) is given a shot at joining an elite surveillance unit as it tries to solve a jewelry store robbery. Squad leader Sergeant "Dog Head" Chin (Simon Yam) isn't sure she has the right stuff for the job. The team pores over surveillance camera footage trying to identify the gang of thieves led by the clever and dangerous Shan (Tony Leung). Painstaking police work combines with intense action as cops and crooks head for a showdown.