Ming (Andy Lau) and Tan (Tony Leung) lead parallel lives: Ming is a Triad mole in the police department; Yan is a police stooge in mob boss Sam′s (Eric Tsang) Triad Gang. Both men have a desire to put their false lives behind them and to take their rightful place in a society that eludes them One night, during a police raid to bring down Sam's Empire, the two men′s paths finally cross. Both the police and the mob soon realise that there is a mole amongst them and a deadly game of cat and mouse ensues. In this race again time nobody is safe, and the lives of everyone involved becomes threatened. In the meantime, Superintendant Wong (Anthony Wong) does his best to keep Yan′s secret safe, but how long can the men′s hidden lives remain undiscovered