This is the Circle — Tash McAdam

In the middle of two wars, including one that they didn't want and didn't ask for, the Psionics of ARC struggle to turn back the Eaters. The Institute is still waiting for an opportunity to regain control of the city, but right now there are more pressing concerns. Outside the Wall, chaos reigns, and the slums are overrun. Citizens and dwells alike are panicked and rioting. Cassandra hides in Epsilon 17's body, convincing those closest to her that everything is normal as she pieces together plans to escape in the confusion. But when the Eaters take her, Thea manages to regain control. The tables have turned. Now she has to pretend to be Cassandra to survive -- but fortunately her time in the Institute prepared her well. If she tries to flee, she'll be killed, but if she stays with the cannibal hordes she's bound to be discovered. Escape seems impossible, but help -- and friendship -- comes from an unlikely source. Toby and Serena have their hands full fighting the invading Eaters and trying to track down leads on where Thea could be. Cut off from his twin, Toby's relationships with ARC deepen and grow, but he's consumed by his guilt and his need to find Thea. The cannibal threat looms ever closer, and with one of their best weapons either lost or disabled, ARC has to decide what their priorities are. Should they try to kill her, or save her?