The Traitor's Son

Ten years ago Jensen Sullivan's father was found guilty of dealing with the demons, and the whole household went down with him. Jensen carries the same charge along with the killing of his own teacher, and he has been moving from place to place since, treating people where he stops. A hundred years before that, seven human sects sealed the gate to the demon world at the abyss across the river, and three swordsmen died doing it. An alliance was set up to hold the border afterward, and the border stayed quiet. Villagers start turning into demons. Jensen looks into the cases and runs into Xavier Lewis, an alchemist his own family has written off, and Keira Yates, who walked out of an assassin organization that now pays for her head. The three of them draw weapons on each other before they work the same case together. It takes them through the politics of the sects and an incursion by the demons, and the sickness they are tracing runs back to the case that was built against Jensen's father.