Aiden Osterberg, a 39-year-old man, is hardened by the rigors of exorcism and his constant efforts to save as many people as possible. He used to be an ordinary man, with an office job, a wife, and plans for the future, but all of this was destroyed by demons who stole his wife's soul, transforming her into an evil, bloodthirsty creature. He was forced to kill her to prevent her from harming anyone else, but that day still haunts him in his most terrifying nightmares. That day marked the point of no return when his life was divided into before and after, forcing him to pursue vengeance and become an exorcist. Now, vengeance has faded, replaced by simple duty. He has forgotten what a normal life is and its simple joys.