Club 99 is not just a hideout for triad gangsters, but also a haven for smuggling jewelleries from robbery. When detective Law is investigating a jewellery heist, he is ambushed by the men from Dog Stone (Sek Yin-tsi) who is the owner of Club 99. Then, Law's daughter Fong (Law Yim-hing) helps her father to be undercover and disguises herself as a dancer in the club and gambler Lung (Lam Kau) is also an informant for the police force. While Dog Stone is cunning enough to discover their identities, there are in fact more undercover agents in the club...Influenced by Hollywood's semi-documentary style, the film has a detailed yet complex portrayal of human nature－undercover anxieties, domineering gangsters and moral ambiguity. With its realistic chasing and action sequences, the film is nonetheless a very entertaining piece of cinema.