The head of an elite Hong Kong surveillance unit (Simon Yam) keeps one eye on his rookie apprentice (Kate Tsui) and the other on a notorious criminal (Tony Leung Ka Fai) he suspects of masterminding a recent jewel heist in this tense thriller from filmmaking duo Johnnie To and Nai-Hoi Yau. Of course, the criminal knows all along he's being watched. But that doesn't stop him from trying to pull off the biggest score of his career.