Blood Moon (Grant & Daniels Trilogy #3)
Charlotte Raine

At the same time, Sarah Latham finds herself joining a cult that believes the end of the world is coming, and their job is to purge all evil from existence. In apocalyptic mayhem, Sarah plays a major part in their plans of murder, while Aaron tries to
track down his son's killer, while also figuring out his relationship with Teresa.
As the perceived end-time begins to creep closer, the only guarantee is that Satan is more than a personification of evil—sometimes he exists inside people, pulling them into the darkness