The Siege of Macindaw: Book Six (Ranger's Apprentice)

The kingdom is in danger. Renegade knight Sir Keren has succeeded in overtaking Castle Macindaw and is now conspiring with the Scotti. The fate of Araluen rests in the hands of two young adventurers: the Ranger Will and his warrior friend, Horace. Yet for Will, the stakes are even higher. For inside the castle, someone he loves is being held hostage. And now the time has come for this onetime apprentice to grow up.