Still reeling from having lost her chance to become a vampire, sixteen-year-old Rayne learns that she is destined to be the new Vampire Slayer and must go undercover to stop a maniacal member of the undead who seeks vengeance and power by spreading a fatal blood disease.

Sunny and her twin sister Rayne travel to Las Vegas, where Sunny's boyfriend Magnus, the leader of the Blood Coven, is attending a vampire convention where he will take a beautiful female as his blood mate.

When Rayne is chosen to track down her twin sister, Sunny, and Sunny's vampire boyfriend, Magnus, for what will mean certain death at the hands of the Vampire Consortium, she and her boyfriend Jareth go deep beneath New York City and through the Gates of the Underworld in hopes of saving them.