First film in the series, based on Ni Kuang's spy pulp novels. Police Commissioner Fong enlists the chivalrous female bandit Muk Lan-fa to retrieve the latest gadget that emits deadly laser beam and its protocol, which allegedly have been transferred away by Ho Tin-hung. Sensing his life in danger, Ho recruits the agent Ko Cheung as his aide, but no sooner has Ko set foot in his house than Ho is murdered. The opportunistic Detective Chan coerces Ko into the hunt by implicating him in the crime. Masking their own agenda, Muk and Ko enter into a duel of wits which leaves the beaten Ko with a counterfeit. Having abducted Muk's mother, Chan presses Muk and her cousin Sau-chen to surrender the genuine article, but Ko unmasks Chan, the spy, by baiting him with the weapon. The police squad led by Fong and Commissioner Suen swarm onto the scene, arresting Chan while he is attempting to flee holding Muk's mother hostage. Chan dies amidst a shower of bullets fired by his own daughter Sau-chen.

Celebrity Sadora is seriously wounded in an air crash. Police commissioner Suen and subordinate Ko Cheung find out Sadora was under duress from the Black Dragon Gang to collude with the criminals who had held his daughter hostage. When Ko, assuming Sadora's identity to safeguard his life, is abducted by the gang, Suen turns to 'Black Musketeer' Muk Lan-fa. By blatantly refusing to cooperate with the authorities, Muk escapes the surveillance of both the police and the gang. Acting alone, she scouts the location of the lair but ends up being imprisoned in the same cell with Ko. The captives use every trick in the book to escape. An undaunted Muk returns to infiltrate the den, while her sister Sau-chen, Suen and Ko are lying in wait. The hostages are released and the gang wiped out in a battle fiercely fought. (Synopsis based on visual audiomaterials)

Ghost-faced To is murdered in a mortuary after paying a visit to Muk Lan-fa. A set of teeth is found missing from another dead body. Lan-fa’s sister Sau-chen follows the leads on a business card To left behind to a dental clinic which suddenly bursts into flame. The news of her sister’s abduction by the infamous Japanese criminal Katsu Saburo soon reaches Lan-fa. Working together with her police friend Ko Cheung to crack the case, Lan-fa analyses photo evidences in minute detail. The duo order the retrieval of a pole that has survived the explosion intact while lying in wait at the clinic. Sau-chen, who has escaped, saves the duo from the chiller where they are detained. Inspector Yeung retrieves the operation plan concealed in the pole and the secret codes in the set of teeth, but the spook is shot dead by Katsu before he could reach the Hell’s Gate and the treasure buried there. Constable Kwan, and others and wipes out the gang at the Hell’s Gate.