Help Me Find This Book! It's really bugging me a lot!!?

I really don't remember much, but it is about a girl who has a pet spider that lives in a matchbox. She is either kidnapped or taken by a family or a cult or something that believes in magic. A boy who belongs to the cult befriends the girl while her spider is tortured so the cult can gain control of the girl. All of the members of the cult have pets or familiars being tortured so they are under control of the boy's father. I think it's his father that is. Anyway, they want to kill the spider so the girl will bond with a wolf that is very strong magically. The boy was supposed to bond with the wolf, but he prefers technology to magic, and is a disappointment to the cult. They run away and land up in another dimension or something, and they're in a type of huge tree where something happens (other people are in this tree too), and they run away because the tree is sick, and they see unicorns somewhere along the wasy. also, the wolf is with the boy and the girl. That's all I remember. tnk
Help Me Find This Book! It's really bugging me a lot!!?
"Spellfall" by Katherine Roberts


http://www.amazon.com/Spellfall-Katherin...


"On a gray, rainy day in England, 12-year-old Natalie crosses a sodden supermarket parking lot carrying a bag of empty beer bottles for the recycling bin. Her attention is caught by a colorful piece of crumpled metallic paper in a puddle. Curious, she picks it up. From this prosaic opening bursts a story that whirls off on wings of fantasy as the bit of litter turns out to be a spell planted by Hawk (the sinister leader of a band of outlaw spellmages) as bait to trap Natalie into becoming the essential 13th member of their spellclave. Halloween approaches, and, during the 24 hours of the Opening, the outlaws plan an assault on the society of true mages who live within a gigantic spelltree in Unicorn Wood. Four teenagers--Natalie, her stepbrother, Tim, her best friend, Jo, and Hawk's fearful son, Merlin--are catapulted into the conflicts of this magical world that lies just outside of ordinary reality. At the same time, while they deal with kidnapping, black magic, unicorns, animal familiars, and the ultimate chemical weapon, they work out more ordinary problems with parents and each other"

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