Ching is a renowned mercenary who, along with Siu-chuen and May-kwan, makes a living by capturing wanted criminals. But a tangled love triangle emerges: [Siu-chuen] is in love with [May-kwan] and has proposed to her, while [May-kwan] loves [Ching] and has long expressed her feelings for him. Old Eagle, a member of the Green Dragon Society, had been blinded by [May-kwan] earlier, and he entrusts his disciple Silver Fox to seek vengeance on her, even if it means paying with his own life.
While picking up Siu-chuen's younger sister, Wai-heung Wai-heung, at a train station, [Ching] decides to propose to [May-kwan]. Yet tragedy strikes when Siu-chuen is killed by Fox while trying to save May-kwan, and Fox is left with a severed eye. Following the suggestion of her older sister May-wai May-wai, May-kwan leaves Ching, claiming she needs time to forget Siu-chuen, though Ching remains haunted by thoughts of her and keeps reaching out to her through her sister. In the meantime, Ching trains Wai-heung to be his assistant and hones his sword skills.
On Wai-heung's sixteenth birthday, the Madam of Pets Madam of Pets hosts a martial-arts contest to choose a husband. May-wai tries to mislead Ching by making him believe the Madam of Pets is May-kwan. Undeterred, Ching enters the contest without an invitation, defeats the Madam of Pets' guards, and defeats the top competitor, Mr Ford. However, other fighters press their own claims to the prize, and the Madam of Pets becomes an object of jealousy. In a moment of chaos, Ching unmasks the Madam of Pets and discovers she is not May-kwan, prompting him to storm out, a move that infuriates the Madam of Pets.
Ching then confronts May-wai for the deception and is knocked unconscious when she shoots him with a Suffocate Bullet. She also tries to lure Ching to New York City, but Fox’s plan continues as Silver Fox infiltrates her home, tapping her phone line and attacking her with a Thunder Bomb. Ching, who had been hiding in May-wai's house to overhear the conversation with May-kwan, learns that his sister May-kwan has been living in the flat across from him.
Ching rushes to May-kwan and calls Wai-heung to join him, though he is a step behind Silver Fox. In their brawl, Silver Fox inhales some Horrible Angel drugs and attempts to use them to turn May-kwan into his slave within 24 hours. Ching arrives just in time to confront Fox and carry May-kwan to the hospital after repelling Fox. Wai-heung, who secretly harbors feelings for Ching, hears May-kwan murmuring Ching’s name as he wakes and discovers that May-kwan never loved her brother but loved Ching all along.
Ching embraces May-kwan and proclaims his love, even as she notes her time is short and asks him to destroy her if her transformation ever begins. May-kwan’s fate becomes intertwined with May-wai’s schemes when May-wai reveals that only the Madam of Pets can save May-kwan. Ching escorts May-kwan to the Madam of Pets’ palace and pleads for help, but the Madam of Pets remains wary and makes him kneel on a trail of shattered glass before eventually agreeing to consider a cure.
Despite this, the Madam of Pets still refuses to rescue May-kwan immediately, and Ching brings her home with a plan to trigger a deadly explosion by turning on the gas pipes when May-kwan becomes a Horrible Angel, hoping they will die together. Yet Silver Fox arrives again at May-kwan’s flat, capturing May-wai and Wai-heung and engaging Ching in a fierce confrontation, exposing Ching to several blows from the Horrible Angel.
Ching manages to wrest the drug away and doses himself, gaining the upper hand as the Horrible Angel within May-kwan starts to take full effect and Fox orders May-kwan to attack Ching. In a desperate move, Ching traverses May-kwan’s body with the drug to suppress its control, then lures Fox back to his flat where the gas pipes explode. As the danger rages, the Madam of Pets and her followers arrive to rescue May-kwan and administer an antidote to the Horrible Angel, pretending to have saved May-kwan so she would shun Ching, though a separate antidote exists for Ching, allowing him to survive by sheltering under a bathtub.
In the end, Ching and May-kwan depart to roam the world together as a couple, their bond tempered by danger, loss, and the complicated web of loyalties and love that surrounded them.
