三十年代的广州,政局动盪,黑道横行。由于鸦片生意利润丰厚,当时政府设立禁烟局,名为禁烟,实则公然贩卖私烟。主治禁烟局的黑帮龙头郑朗军(岳华) 的长女郑九妹(邓萃雯) 突然从上海回来,希望染指鸦片生意,九妹为人心思慎密,做事心狠手辣。刑侦队长刘醒(黎耀祥)一生劳碌只求家人安稳过活,特别是身患重病的妹妹刘晴(陈法拉)最令他牵肠挂肚。刘醒性格暴躁,但为人重情重义,爱手足,爱邻里;在一次生死关头,为保胆小怕事的手下唐吉(敖嘉年)差点断送性命。

九妹与刘醒在人生轨迹上交错相遇,共同历经多次劫难,二人似是命中注定的天敌,彼此不退不让,却在不知不觉间培养了一份不言而喻的默契及微妙的感情关係。至后来日本侵华,广州沦陷,九妹被姑姐郑朗喜(谢雪心)设局陷害,刘醒伴着九妹共同渡过了人性最凶险的黑暗岁月……

Guangzhou is in a state of political turmoil in the 1930s. Gangsters go on the rampage; opium trading is rampant too. Seeing the huge profits illicit opium trading brings, the government has established the Anti-Smoking Bureau under the guise of suppressing opium. Gang kingpin Cheng Long-Kwan (Yueh Hua) heads the bureau. His eldest daughter Cheng Kau-Mui (Tang Shui Man) returns from Shanghai so that she too can take a share. Kau-Mui is an unscrupulous person who meticulously plans her every move. Lau Sing (Lai Yiu Cheung) is the leader of the Criminal Investigation Team. He has worked hard all his life to bring an easy life for his family, especially his bed-ridden younger sister Lau Ching Ching (Fala Chen). Despite his hot temper, he values friendship and brotherhood more than anything else, to the point that he once almost sacrifices his life to help his team member Tong Kat (Pierre Ngo), who is a timid person.

It is fate that Kau-Mui and Lau Sing should meet each other and survive many calamities together. It is also fate that they are like natural competitors who will never give in. Mutual understanding and affection grow slowly between them. Later, the Japanese army comes and Guangzhou falls into the hands of the Japanese. Kau-Mui enters the darkest time in her life when her aunt Cheng Long-Hei (Susan Tse) frames her up. Fortunately, Lau Sing is always by her side…