a vampire prince fall for a human girl and unaware that her brother be a famous vampire hunter . that the underlying theme of this martial art romp which borrow idea from underworld and buffy the vampire slayer but manage to maintain a style of it own . i be bemuse by the uk and hong kong title the twin effect a there be no twin involve in the story . it turn out that the two main female character be play by hong kong pop star who perform a the twin . don not let this put you off . these girl can act ( at least well enough for this type of film ) and add a lot of charm to the proceeding . jackie chan turn up for a couple of cameo appearance add a dash of his own brand of slapstick mayhem to the proceeding . all in all this be great fun for those who like their vampire serve up with a help of tongue in cheek humour .