Tony Thompson (JONATHAN LIPNICKI) is a nine-year-old who's moved with his mom, Dottie (PAMELA GIDLEY), and dad, Bob (TOMMY HINKLEY) from San Diego to Scotland where the latter is designing a golf course and convention center for Lord McAshton (JOHN WOOD).
Tony isn't happy because he doesn't have any friends, and his parents are worried about the many nightmares he's been having that are always about vampires. To make matters worse, nobody believes his stories about such creatures and even McAshton's two grandsons pick on Tony in school.
Things change when Tony meets Rudolph (ROLLO WEEKS), a young vampire who mistakes Tony for one of his own when flying by one night. Weak from a lack of plasmatic nourishment and initially unhappy to have met a human, Rudolph realizes he shares a kindred spirit with Tony and is happy when he finds him a cow to satiate his appetite.
It turns out that Rudolph, along with his aristocratic parents, Frederick (RICHARD E. GRANT) and Freda (ALICE KRIGE), sister Anna (ANNA POPPLEWELL) and rebellious older brother Gregory (DEAN COOK), don't want to attack humans, but instead want to become them. Unfortunately, for the past three hundred years they've been searching for a missing amulet stone that, when used upon the rare alignment of the moon and a certain passing comet, will turn them back into mortals.
Worse yet, Rookery (JIM CARTER), a persistent vampire hunter, is hot on their trail, determined to kill them the old fashioned way - with stakes - or via the missing stone that, when used in another amulet, will send them straight to Hell. From that point on, Tony tries to do what he can to help Rudolph and his vampire family while they all try to avoid Rookery and the light of day.