A.D.2010, sponsored by Tin Wai Pharmaceutical Factory, Dr Cole, who is a Biochemist and Pathologist, is undergoing an illegal experiment, which is to raise a Snake-woman Siu Ling by merging human genes with snakes' venom. Siu Ling is brought up to rescue Ho Tin who is the only son of the Factory owner. Ho Tin is afflicted with severe blood cancer.
Two murder cases are uncovered in crowded urban area of Hong Kong. The victims are both CEO of the Ba Kei Group and the course of death are snakebites. Kwan Wai, the detective, is very suspicious of Model Maria, who might be the Snake-woman raised by Dr Cole. And he is also suspicious of Ching Bo, who is the assistance of Dr Cole. Ching Bo might be the one pulls string behind the scenes. Unfortunately, he is lack of evidence. Soon, Dr Cole dies from snakebites, which assures Kwan that Maria is the murderer. Later he finds out that Maria is not the Snake-woman but Dr Cole's illegitimate daughter.
Ho Tin, who is Kwan Wai's best friend, meets a young lady Siu Ling and then falling love with each other. Kwan Wai happens to see the frightening progress when Siu Ling turns into a python and slips away. After knocked down by the policewoman named Li Hung, Siu Ling is brought to the private laboratory where she finds out the truth of herself being a medical material for curing Ho Tin. She is accused of homicide following. During the detention she accuses that Li Hung as the real Snake-woman. Nevertheless she realizes that the policewoman Li Hung has eaten by the Snake-woman, and Li's body is used to commit murder. It is astonished that Dr Cole is actually an unscrupulous manipulator. Does Dr Cole fake his death in order to conceal himself from the police?