影片背景是英国殖民香港时期。少女左兰命运多难，也遇到了铁腕大佬陶天罪之后一步步陷入犯罪漩涡以及爱情之中，同时进阶成为江湖一姐的传奇一生

左兰年轻漂亮，原本也是纯洁善良的女孩，有一个相恋多年的男友，却因为父亲嗜赌成性，被追债时左兰惨遭凌辱，本以为男友会对自己不离不弃，却将自己送上了老板的床，最终左兰心如死灰。

九龙寨的老大救下轻生的左兰，左兰因为自己的人生被毁掉，想要报复毁掉人生的一种坏人决心，跟随着九龙寨老大在不断的历练之中，手刃九龙寨徒也成为了江湖大嫂在接受九龙寨生意之后，设计杀死所有伤害过自己的人和贪污黑警。九龙寨老大罪哥多年，手下陈杰一直暗恋着左兰，看到左兰如今的变化，也十分痛苦，希望左兰可以回头，在最高弥留之际想要传位于左兰告知陈杰是警方卧底，这时香港政府已经着手清理九龙寨在内患外忧之际，左兰会有着怎样的抉择？

The background of the film is the British colonial period in Hong Kong. The fate of the young girl Zuo Lan was very difficult, and she also met the strongman Tao Tianzui. After that, she fell into the whirlpool of crime and love step by step, and at the same time advanced to become a legendary life of a sister in the world.

Zuo Lan is young and beautiful, and she was originally a pure and kind girl. She has a boyfriend who has been in love for many years, but because her father is addicted to gambling, Zuo Lan was brutally abused when she was in debt collection. She would never leave her, but she sent herself to the boss's bed. In the end, Zuo Lan's heart was ashamed.

The boss of Kowloon Walled saved Zuo Lan who committed suicide. Because her life was ruined, Zuo Lan wanted revenge for destroying her life A kind of bad guy's determination, following the boss of Kowloon Walled in constant experience, and killing Kowloon Walled disciples has also become the sister-in-law of the rivers and lakes. After accepting the business of Kowloon Walled, she designs to kill all those who have hurt herself and corrupt black police. Brother Zui, the boss of Kowloon Walled, has been secretly in love with Zuo Lan for many years, and his subordinate Chen Jie has been secretly in love with Zuo Lan. It is also very painful to see Zuo Lan's changes. Undercover, when the Hong Kong government has started to clean up Kowloon Walled's internal and external troubles, what choice will Zuo Lan make?