Clem gets a call that is every mother's worst nightmare. Her nineteen-year-old daughter Erin is unconscious in the hospital after a hiking trip with her friends on the remote Orkney Islands that met a horrifying end, leaving her boyfriend dead and her best friend missing. When Erin wakes, she doesn't recognize her mother. And she doesn't answer to her name, but insists she is someone named Nyx.

Clem travels the site of her daughter's accident, determined to find out what happened to her. The answer may lie in a dark secret in the history of the Orkneys: a woman wrongly accused of witchcraft and murder four centuries ago. Clem begins to wonder if Erin's strange behavior is a symptom of a broken mind, or the effects of an ancient curse?