Astrid was brought back six months ago for one purpose: to help restore balance in the city.Cursed with a past she can barely remember, Astrid fills her role as an assassin with ease. Every day, she kills Unworthies – those deemed unfit to be a part of the society so carefully constructed after the Infirmum swept through the earth a hundred years ago, leaving all of the children dead and all of the adults infertile. Humanity now relies on a weekly injection of Curat to survive. Everyone is young, beautiful, and almost immortal – including the enigmatic doctor who renewed her, Michael. As the city is pushed into a new ice age, Astrid realizes she knows dangerously little about the place she lives and the people she kills for. Her trigger finger begins to fail her, and she fears she might be labeled as Unworthy next. When Michael draws her into a rebellion, secrets begin to come out, and the worst one might belong to the past she forgot. As she starts to remember and Michael tells her the true reason he’s been able to survive for so long, Astrid finds out she won’t just have to save the city, she will also have to decide what it truly means to be human.