Ranger's Apprentice 2, The Burning Bridge

As the Kingdom of Araluen prepares for war against Morgarath, Will and Horace accompany the Ranger Gilan on a mission to Celtica. But Celtica's villages and mines are silent. Only an exhausted and starving girl called Evanlyn can tell them why: Morgarath has sent his foul creatures to enslave the Celts. While Gilan rides swiftly back to Araluen to report this news to the King, Will and Horace discover the true purpose behind Morgarath's actions. The Kingdom is sure to be defeated in a surprise three-sided attack - unless they can find a way to prevent it.