Gangster Pang Tin-tak runs an underground casino operated under the guise of the Blue Nightclub. The fearless and cagey Fung Kim-ching and the adept professional To Yuet-hung strut their stuff on the poker table and catch the eye of the boss. Enlisted as his trusted aide, To the undercover officer carefully cloaks her identity to conduct a criminal investigation but has to stop in the light of Pang’s growing suspicion. The raid led by Detective Chan is successfully foiled by the sly gangster, who unmasks the spy and holds her captive together with Chan. Fung frees the captives before he joins Pang for his transactions by the sea. Pointing a pistol at the gangster, Fung identifies himself as the leader of the Interpol anti-drugs squad as the gang members are handcuffed and led away by To and her team.