No one knows how to help Dara control the power running through her veins. If she can't tame the raw energy of the Ancient Blood, it will burn her out. Auhle is her last resort. But he is up to something. A no-good something. And like everyone else, he's got a price-one that Dara isn't sure she's willing to pay.
Caspian, Mac, Roan, Elnor and Jaem race back to Kaleb's desert lab for answers, only to find that they are too late. Now they have to convince the enemy of their enemy to be friends. They try to enlist the dysfunctional Watcher Society to unite against the threat posed by Auhle. Even then, no one knows if their numbers will be enough to stand against the black army under Auhle's command.
All converge upon the Airen Islands and an abandoned Temple of the Ancients for the final battle to decide the future of humanity and the Ancient Blood.