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.

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.