Nick Chen (Chow Yun-Fat) was the first Chinese-born immigrant in the NYPD, and is now one of the force's most decorated officers. As such, he's been named leader of the city's Asian Gang Unit, who are the primary peacekeepers in Chinatown. Trouble has just arrived for the Triads, the long-entrenched Chinese gangsters who are the real power behind Chinatown. After years of posing as honest businessmen, the Triad's powers are threatened by the newly arrived Fukienese Dragons. With a gang war on the horizon, the city sends a new recruit, Danny Wallace (Mark Wahlberg), to join Chen's unit. Danny finds Chen and the AGU in a very comfortable (perhaps too comfortable) relationship with the Triads. When the mobsters attempt to corrupt Danny, Chen must reassess his relationship with the Triads, and Danny must also learn that certain concessions must be made to ensure the peace in this world set apart from the rest of New York.