The Golden Key (1978)

Various distinguished members of Hong Kong high society were being blackmailed by mysterious and attractive lady Chang Siu Juen, who seems to know the secrets of their past and present illegal activities. Millionaire Cheng Yung Seng knew that it would be his turn next. He thus planned to eliminate Chang first but the plan did not work out and Chang was saved by private detective Fang Dai Kuen...