Namina and Simone are vigilante partners who lure suspected predators to their deaths. When a plan goes awry and a serial killer nearly murders Namina, she makes a desperate plea to survive. Her call is answered by Keres, a Ker-an ancient Greek death spirit and daughter of Nyx-who offers her life in exchange for a soul. Namina agrees, killing her attacker and unknowingly binding herself to a supernatural contract: to deliver the souls of evil men to Keres in perpetuity.
Over the next twenty years, Namina becomes a reaper of the wicked, wielding divine strength and immortality. She and Simone live in isolation, suspended between worlds, as Namina hunts predators and feeds their souls to Keres.
Their world turns on its head when Namina is sent to kill an Empusa, a mythological creature who seduces and tortures women-and she is forced to confront the limits of her moral code. After a brutal battle, Namina has no choice but to ask even more of Keres-only this time, the price isn't one that Namina is willing to pay. Now Simone's soul is also on the line, and Namina must accept the bargain if she is going to survive. In order to save the one she loves, can she kill the god she is bound to, before her luck and the clock runs out?