Guangzhou is in a state of political turmoil in the 1930s. Gangsters are on a rampage and opium trading becomes rampant. As they watch the illicit profits from opium trading escalate, the government forms the Anti-Smoking Bureau under the guise of suppressing opium, but the bureau is under the influence of Cheng Long-kwan, the gang's kingpin. His eldest daughter Cheng Kau-mui  who is an unscrupulous person soon returns from Shanghai to reap the rewards. Mui meticulously plans her every move. On the other hand, Lau Sing  is the leader of the Criminal Investigation Team. He has worked hard all his life to ensure an easy trail for his family, especially for his bed-ridden younger sister Lau Ching. Despite his hot temper, he values friendship and brotherhood more than anything else. Once, he almost sacrificed his life to help his timid teammate, Pai Kuat. Meanwhile, the Japanese army invades China and Canton falls into the hands of the Japanese. Mui enters the darkest time in her life when her aunt Cheng Long-hei frames her.