This is Book Four in the Ranger’s Apprentice Series by John Flanagan.
The Review in Booklist:
Following Will and Evanlyn’s escape from slavery in The Icebound Land (2007), Halt determines that the Temujai mean to attack Araluen and decides to help the Skandians defend their land. Rejoining Halt, Will and Evanlyn become warriors in the stronghold where they had recently been captives and use their wits and skills to fight the common enemy. The story plunges forward with irresistible narrative drive toward the climactic battle scene. Even readers drawn to the series for its deftly drawn characters and setting may find themselves caught up in the action. A fine entry in the increasingly popular Ranger’s Apprentice series.
Amazon has identified copies as “Bargain books” books that are new but could include a small mark from the publisher and an Amazon.com price sticker identifying them as such. They are selling the paperback for $3.20.