Eye in the Sky takes place around the darker side of Hong Kong society, where the story begins with a group of organized burglars successfully robbing a jewelry store. The plot begins with the wet-behind-the-ears new recruit Piggy (Kate Tsui), who is plunged at the deep end in her first surveillance assignment working alongside her mentor, Sergeant Wong (Simon Yam). Both of them worked for the Hong Kong police elite surveillance unit. After reviewing the jewelry store surveillance videos, an attempt was made to track down one of the robber. An undercover crew was setup, and blended right into the population. Fatman (Lam Suet) went about his business without knowing every one of his move was being trailed by the surveillance unit. His identification was revealed with the use of an octopus card. A police unit ambush was established at the next robbery plot, except the plan was spoiled when the elusive Chan (Tony Leung Ka-Fai) figured out they were being tailed. As the robbers tried to escape, the surveillance activities turned into a showdown with the HK police tactical units. The remaining robbers would continue their escape, while the surveillance unit continue to blend into the background and try to track them down using spy gadgetry and realistic surveillance hi-tech.