When the worlds of Ranger's Apprentice and Brotherband cross over, action and adventure are guaranteed! King Duncan of Araluen has an urgent mission for Hal and the Heron Brotherband. One assassination attempt on Princess Cassandra was foiled. But the killers won't be satisfied until they have fulfilled their honour-bound duty. The Herons, along with Ranger Gilan, set off for Arrida. There they must track the cult of killers across the desert, and infiltrate the cult's mountain lair to find their leader and stop him. But the giant assassin isn't the only threat they will face. There is a seaside battle looming, and the Herons are called upon to help an old friend of Araluen in his fight. Trapped in an unfamiliar land, their forces split between searing hot land and treacherous seas, can the Herons complete their mission before the killers find their royal target?