Trapped in the doomed city of Atheia while the fate of the Valley is decided by two raging armies, Thorn is haunted by the dangerous and mysterious object of power known as the Crown of Horns. Guarded by dragons, the Crown of Horns is the only thing that Thorn believes can stop the Locust and end the war... but how, and at what price? Fone Bone believes he knows what the price will be, and he must decide where his heart truly lies...