An operation in Thailand against a notorious drug lord changes the destiny of a Hong Kong Police Department narcotic team. Five years later, a drug dealing brings them together again.

A financial tycoon, once a triad member, tries to eradicate the drug market while an old accomplice aims to be Hong Kong's first drug lord.

Hong Kong police agent Cheung (by Aaron Kwok) works undercover in Kang’s (by Sean Lau) drug cartel, while another undercover cop Au (by Louis Koo) successfully earns their trust in an incident, a brotherly-bond is built among the three. After the Police busts the syndicate in Hong Kong, Kang subsequently hides away in the Golden Triangle, by chance he receives a tip-off about the betrayal within his circle of trust…