Cassie and Laney fancy themselves amateur ghost hunters. When a carnival comes to town, Cassie embraces the chance to try something new. Carnival workers watch the girls with a collective gaze that ignites in Laney a dark and dangerous fascination, leaving Cassie unnerved. It's not just their age or the unsettling way they stare. There is something in the shifting of their skin and the way their features seem to change in the shadows. Cassie can't shake this sickening feeling that there's more to the carnival than meets the eye. When townspeople suddenly start dying and bloody warnings appear around town, Cassie is lured into a nightmare where trees whisper and strange, shape-shifting men haunt the backwoods she once hunted for ghosts with her best friend. Then Laney goes missing, and only Cassie can get her back. But the creatures of the trees aren't simply going to hand Laney over to Cassie without getting something in return.

It’s only a matter of time before he gets what he’s come for. Cassie Harris has turned her back on best friend Laney Blake. She had no other choice. Laney is one of them now, a creature of the trees. As Cassie’s senior year wears on, the woods grow quiet, snow blankets the ground, and the murderous beings who once taunted her have drifted away like the brittle leaves of Fall. Though the woods no longer stir with rushed whispers and wind-blown laughter, the fear remains. No one understands this fear better than Cassie. She wishes she could tell them not to worry. After all, the shape-shifting men of the trees and the women who travel with them, seeking out girls to abduct from carnivals, are gone. And the one that stayed behind? He isn’t interested in anyone but her. Now, Aidan’s interest in Cassie is a chilling reminder of the what lurks at woods edge. He stalks her home, her school, her bedroom. He won’t stop until he can find a way to lure Cassie into the forest to become one with him forever.

The faery queen has forbidden Aidan from stalking his prey, but Cassie should have known that nothing would keep him from what he wants: to steal her away forever into the realm of the Fae. Cassie struggles to pick up what’s left of her life, keeping true to her promise to watch over her best friend’s son. But despite the faery queen’s promise of safety, the shadow of Aidan is ever present in her mind, haunting her dreams and turning forest shadows into nightmares. The rest of her friends are getting ready for college, but not her. The Fae haven’t left yet. Cassie knows because Laney lingers still, drawn to the son she gave up, the foliage at his window sill bright green and flourishing at her touch. Laney’s son is safe in the arms of his adoptive parents, and the babe has Cassie to watch over him from afar. That should have been enough for the new faery, but it wasn’t. She couldn’t let her son go. Laney watches him from afar, motionless, ageless, addicted to his tiny movements and contented sighs. The thought of leaving him is unbearable, even if she knows leaving is the only way to keep her best friend safe from Aidan’s grasp. When the faery queen’s threat of departure becomes all too real, Aidan takes matters into his own hands, throwing the Fae into a battle that risks their very existence. His action impels Laney to choose which side she really belongs on—human or faery—and forces Cassie to decide just who she can trust, at last, with the truth.