The cops have planted a mole in Hong Kong's nastiest Triad group. The Triads have planted a mole in the police force. Each infiltrator has to find the other without losing his cover, and his life. This idea so simple, so reverberative sets up a thriller rooted in character, as nooses tighten around the two rogues (Tony Leung Chiu-wai, from Hero, and Andy Lau, from Daggers), testing their loyalties to the organizations that bred them. This splendidly tense melodrama, directed by Andrew Lau (no relation to Andy) and Alan Mak, is to be remade by Martin Scorsese with Leonardo DiCaprio and Matt Damon. It might be great, but why wait? The unimprovable original is out on DVD. See it with someone you think is a friend.