In 1981, eleven-year-old Agnes Hellaire lives with her troubled parents in the dark Redwood Forest. As her parents' marriage continues to crumble, Agnes is approached by a magical black cat that is more than it seems. It offers to solve all her problems, and she gladly accepts. However, as people close to Agnes begin to disappear; she realises there's something dangerous lurking in the trees.

Over twenty years later, Agnes is infamous as the lone survivor of a ruthless mass murderer that was never caught. Despite the nightmare of her childhood, she has managed to find some semblance of peace. Until the killings suddenly resume, and another young child emerges from the forest, covered in blood.

As she slowly begins to descend into madness, Agnes begins to realize that Cat's 'help' came with a price she is unable to pay and that the dead bodies will not stop until she fulfills her side of their deal.