After incident, she starts to exhibit angry and short-tempered behavior, the complete opposite of her usual behavior.
Her father David is struggling to make ends meet, while her 14-year-old brother Hunter drives the family crazy with gory pranks. They inherit their deceased mother's Great-Uncle Dragomir's castle in Wolfsberg, Romania after getting a package in the mail. After arriving in Wolfsberg, they meet the strange and steely castle housekeeper, Madame Varcolac.
One day while snooping around Dragomir's lab, Jordan steps on a vial of strange liquid. Hunter manages to pull the pieces out from her foot, but Jordan's behavior changes, such as her allergies disappearing, seeing without glasses, and smelling things very far away. Jordan continues to succumb to the changes, having behavioral changes. After her date with Goran, the young butcher, Jordan turns into a werewolf, which Hunter witnesses. She flees and Hunter contacts his friends for help.
They find Varcolac, who reveals that Dragomir was also a werewolf and was the "Wolfsberg Beast"; protector of the castle and Wolfsberg itself. Vampires have attempted to take over the castle, but Dragomir stopped them before he was ultimately killed. Before his death, Dragomir was working on a possible cure to lycanthropy. However, it will take time to gather the ingredients. Paulina offers the siblings a ride home, but Jordan struggles in trying to resist her transformation. The car breaks down and the Vampires come out, along with Paulina, who is a Vampire. As it turns out, she killed Dragomir to get the manor and will now kill Jordan. Jordan and Hunter are locked in the trunk and brought to her hideout, where Jordan succumbs to the change and is restrained. Hunter leads David to the hideout as they witness Paulina attempting to kill Jordan.
The werewolves attack the Vampires before witnessing the rising sun. They use this to their advantage and kill them with the sunlight, with Jordan defeating Paulina in a final showdown. Jordan and Hunter return to the manor, where Hunter's blood is used in the antidote, which successfully cures Jordan. Varcolac is allowed to continue working there, and gives the Sands the money they inherited from Dragomir. Hunter also becomes the Wolfsberg Beast to take Dragomir's place.
The family returns to California where Jordan demonstrates a new confidence and power at school, and Goran transfers to be with her.