When a pervasive fog grips the town of Fort Johnson, and ancient evil emerges, its sights set on Agnes Blackwood. When she is ripped from her house by an inhuman tree monster, she is besieged by supernatural torment, a message repeated by those that have been trapped before. "Don't submit to him," is written on walls, carved into trees and whispered on the wind. However, as the torment increases and her husband, Artemis, cannot reach her, she struggles to fight against the warning she has been given.