As early as in the beginning of the 1960s, before the “undercover genre” has attained popularity in Hong Kong cinema twenty years later, Ng Wui and Cheng Kang have already explored such a theme (and a female undercover agent actually!). Beginning with the mysterious woman Pak Yuk-sheung’s (Patsy Kar Ling) intrusion into a hotel at  the middle of the night and asking the manager Cheung Wan-fung (Keung Chung-ping) to pass himself as her husband so that she can escape Inspector Chan’s (Chow Chung) chase, the film unfolds with much suspense. Cheng Kang deliberately leaves the audience hanging with many twists and turns in the plot. Aided by Ng Wui’s adroit craftsmanship, the film contains no dull moment and exudes an air of noir sensibilities. Different from her usual elegant screen image, Patsy Kar Ling plays in this film a brave policewoman who infiltrates a drug cartel single-handedly and instigates inner conflicts among the criminal enterprise’s leaders. She remains calm and reveals her quick wit when facing people’s trials and threats during the drug deal. In the end, she uproots the whole drug-dealing enterprise ju st as competently as her male counterparts.