During the wake of the first World War the gap between the rich and poor has started to widen as crime rises and sins grow. As dark times loom over New York City demons have been coming to the surface into the world of man. In order to fight these demons an organization known as the Order of Magdalene seeks to protect man kind by exorcising the evil. In the order Rosette works as an exorcist with her soul-bounded demon partner who has been together since children. While they work together as exorcist they are driven by a dark past where Rosette's brother Joshua has been taken away by the sinner Aion.