Kira Walker: A brilliant medical intern and a hopeless idealist, Kira can’t sit on the sidelines while something bad is happening: she has to get in there, no matter the consequences, and help people. Even her enemies.

Marcus Valencio: Kira is the craziest part of Marcus’s life; if he had his way they’d work together in the hospital, get married, and die of peaceful old age. Things do not work out this way, and he’s thrown into one danger after another, surviving with a constant stream of sarcastic wit.
Samm: Created in a lab, trained as a soldier, and thrown into the front lines of the Isolation War, only to come home to a country that didn’t want him anymore. He is fiercely loyal, sometimes to a fault, and despite his silent nature he feels passionately about many things—including Kira.
Heron: A super-powered assassin without a conscience, viewing humans and Partials alike as little more than tools she can use for her own purposes. With the world collapsing around her, the only purpose she has left is survival.
Ariel McAdams: Ariel is angry: at the woman who betrayed her; at the people who got her pregnant knowing she would lose the baby; at two different species that both seems to have abandoned her forever. She may not be able to save anyone, but at least she can get some revenge.