San Francisco, 1878. Ah Sahm, a newly arrived Chinese immigrant with serious fighting skills, is introduced to Chinatown's most ruthless tong, the Hop Wei, by Chao, a fixer. After impressing Young Jun, son of tong leader Father Jun, Ah Sahm is branded and taken to a brothel, where he befriends Ah Toy, a courtesan with connections. Later, in search of a woman who left China two years earlier, Ah Sahm crosses paths with Mai Ling and Li Yong, followers of the rival tong leader Long Zii, who is trying to avoid an opium war with the Hop Wei, a war that Walter Buckley, ...
Intercepting a shipment of opium at the docks, Young Jun, with Ah Sahm and his Hop Wei lieutenant Bolo in tow, decides to send a message to Long Zii. Big Bill and Lee investigate a grisly murder scene in an alley next to an Irish bar, The Banshee. Penny Blake, the young wife of San Francisco's mayor, finds herself in a bind while visiting the wharf with her Chinese manservant, Jacob. Ah Sahm pays a steep price for playing the hero. The Long Zii clean up a mess, and brace for more bloodshed.
Big Bill discovers a possible solution to his gambling excesses; Penny reveals the circumstances that prompted her to marry Mayor Blake; Mai Ling offers Ah Sahm a way out of a protracted and bloody tong war.
After a bloodbath, the Hop Wei and Long Zii consider a novel way to end hostilities; Ah Toy and her business partner hit a fork in the road; Mai Ling warns her brother against waging a battle he may not win.
Chinatown gathers to witness a "prize fight" between elite warriors from the Hop Wei and Long Zii. Buckley plays a bluff in hopes of getting Mercer to lower his fee. Ah Sahm remembers his roots as a fighter, as Ah Toy warns him of the dangers that await. Bill and Lee question Wang Chao about the recent series of sword killings in San Francisco.