Charged with as much psychological depth as gun-slinging violence, Johnny To and Wai Ka Fai's slick thriller brought a welcome jolt of adrenaline to the moribund Hong Kong action genre. Cool professional killer Ono, aka "O" (Takashi Sorimachi), and brash newcomer Tok (Andy Lau) are both hired assassins, but their styles are worlds apart. O, generally considered the top killer in the East, kills with stealth and precision and wants nothing more than to remain in the shadows. His true identity is a mystery to Interpol agent Albert Lee (Simon Yam), who has been doggedly pursuing O across Asia, and even his known address is a ruse. After running afoul of a powerful crime...