Mou Gaan Dou plot
"Loyalty. Honor. Betrayal."
Yan (Tony Leung) is an undercover agent with the Hong Kong mafia triads. After ten years of hard work, he finds himself deep inside Hong Kong's most powerful gang. Ming (Andy Lau) is a criminal police infiltrator, who was placed there when he was eighteen. With his exclusive contacts in the triads, he soon rises to head of the Criminal Intelligence Bureau. Both men feel increasingly trapped and wedged between good and evil and are only shadows of themselves. One evening, Ming is ordered to arrest the boss of his own triad, while the vital information comes from Yan, the same boss's closest confidant. As the operation progresses, it becomes clear to both sides that there is a traitor in their ranks.