Cop Sam Hui gets picked up by two gorgeous women in a bar and ends up having an intense sexual encounter with one. They are interrupted by a phone call from the scene of a grisly murder. The crime is just one of a series, and the investigation leads Sam to an Insurance Company where the two girls work. Penny (Carrie Ng) fascinates him, even when he discovers that the girls are selling sex in return for favours. Meanwhile, Wendy, has set out to steal Penny's clients by offering them kinky sex. Penny starts to go off the rails as her clients defect to Wendy, and Sam finds out she is addicted to a weird snake serum drug. When he discovers that all the murder victims have a snake DNA in their blood his suspicions turn to the object of his sexual obsession - but it seems she has the perfect alibi... .