Acton is gone, and renegades are dying. Watchers are being murdered for protecting them. 
With nowhere else to turn, Zach has started a trek to find the gates of Apollyon and resurrect his fallen mentor. Ember is along for the ride, and so is the latest island visitor, a timid and unassuming watcher named Theo. 
She knows that she knows him from somewhere, but she's never met him before. Eli seems certain that he isn't who, or what, he says he is. 
When Paul succumbs to an illness no one has ever seen before, things get desperate. As the bonds of the community begin to break, people start to suspect that Ember isn't who she thinks she is, either. 
An old superstition about a rogue watcher will change everything, and everyone, forever.