Ace vampire slayer Reeve (Ekin Cheng) tracks his arch-enemy, the Duke Dekotes to Hong Kong. The Duke is hunting for Kazaf (Edison Chen), the fifth prince of the vampire nation. With Kazaf’s blood and the ancient vampire bible, the Duke will bring a new age of darkness. On arrival, Reeve learns that he has a new partner, a feisty but inexperienced young beauty named Gypsy (Gillian Chung).
Matters are further complicated when Reeve’s innocent younger sister, Helen (Charlene Choi), develops a romantic relationship with Kazaf. With all the odds against them, our heroes get some unexpected help in the form of high-kicking paramedic Jackie Fong (Jackie Chan). In a high impact final reel, Reeve, Gypsy and Helen join forces to fight the Duke and his minions¡K Horror, comedy and high impact martial arts action collide in ‘The Twins Effect’.