Twelve-year-old Hayder Hennessey wants to be a good son for his struggling mother and have a new start at a normal life, especially after the deaths of his father and baby sister. But when his mother moves them from Dallas to the small town of Black Knot, Oklahoma, Hayder figures out pretty fast things are a little bit different here. A little bit off.

Enter Cora Corbucci, Hayder's new next-door neighbor. The sole survivor of a grisly mass murder, Cora has been seeing and hearing a lot of unsettling things lately. Soon, Hayder begins to see and hear things too-unreal things that can't be disbelieved. Meanwhile the citizens of the Knot drift through their lives, blissfully unaware of the slow poisoning of their souls. Of their blood.

Hayder and Cora join forces with Juston Matheson, the town sheriff, to unearth the source of these horrors, exhuming dreadful secrets about their hometown better off having stayed forgotten. An ancient family of witches, the Fulcis, seek to open a door into another realm, a door hidden away in the dark forests and hollers around Black Knot, allowing the awakening of a sleeping horror who seeks to bring about hell on earth.

Only, the gang learns these witches may not be the only evil they must face to survive. For in the town of Black Knot, where every day feels like Halloween, of eternal twilight, Hayder and his friends are about to go to war.