The Keeping Place (The Obernewtyn Chronicles)

When one of their number is kidnapped, Elspeth and the Misfits are forced to use their extraordinary mind powers to help the rebels in their struggle to overthrow the oppressive Council. But Elspeth has another problem to solve - she is still on her quest to destroy the Beforetime weaponmachines. To find a clue hidden deep in the past, Elspeth must travel the Dreamtrails, but her journeys are fraught with danger as she battles a terrifying winged beast intent on destroying her. Gradually Elspeth realises that her quest will take her back to Obernewytn, and it is here, in its past, as well as its future, that the answers lie.