Maddigan's Fantasia by Margaret Mahy
In a time not far from our own, a colourful group of travellers braves the twisting, unpredictable landscape of a world trying to remake itself years after near-destruction. They are the magicians, clowns, trapeze artists and musicians of Maddigan's Fantasia, healing the injured land with wonder and laughter. Garland Maddigan, the 12-year-old daughter of the Fantasia's ringmaster, has been on many journeys before. But she soon realises that this one is going to be very different. For three mysterious children have joined the Fantasia - children with uncanny abilities and a secret past. And with them they bring powerful enemies who will stop at nothing to hunt them down. Soon Garland finds herself embroiled in a series of terrifying adventures that will take her within perilous underground tunnels, through the land of the Witch-Finder and across time itself . . .