Sixteen year old Tom Clarke is a wizard - like his late mother and his grandma Ursula but not his father Michael who disapproves of his son using magic to help his school football team. On a field trip to standing stones Tom and his friend Ben find a magic ring,dropped by father and son wizards abducted by the Nekross,aliens who have come to Earth to extract magic from its practitioners. One of the Nekross,Varg,arrives on Earth and captures Tom and Ursula,imprisoning them on their space craft.
Tom manages to teleport himself back to Earth and,accompanied by Benny,enters Ursula's secret magic chamber,where they meet Randal Moon,a hobgoblin attendant on Ursula. Randal casts a spell which takes the boys and Michael to the standing stones where the space ship landed and transports them to the Nekross craft. Although wizards can only cast three successful spells in one day the ship has orbited the Earth and arrived at a new dawn,allowing the group,along with the captive wizards,to magic themselves back to Earth.
Ursula and Randal cast a shrouding spell to shield earthly magic from outer space but the Nekross send a ferocious cat-like creature - the Grazlax - to hunt down Tom when he is at Benny's house. They lock it in the shed whilst Tom casts a spell to divert Benny's parents but when it escapes they force it to retreat,using a hair dryer which kills it.. Unfortunately three more Grazlax babies are released.
The boys are besieged by the new crop of Grazlaa who multiply with heat and seem likely to reproduce into millions. Whilst Tom gets rid of school-mate Katie,who has come to the door as a charity collector,Benny works out that the creatures are allergic to high pitched noises and destroys them with his violin playing - spattering the house with their insides. They bring Ursula in to effect a magical clean-up,which also turns the reproduction ornaments into valuable originals.