All sixteen-year-old Heather MacNair wants is to feel normal, to shed the intense paranoia she's worn all year like a scratchy sweater. Ever since her compulsion to self-harm came to light, Heather has been kept under her doctor's watchful eye. Her family thinks she's better - and there is nothing she wants more than for that to be true. She still can't believe she's allowed to spend her summer vacation as she always does: at her aunt's home in Scotland, where she has lots of happy memories. Far away from all her problems save one: she can't stop carving the Celtic knot that haunts her dreams into her skin.
Good friends and boys with Scottish accents can cure almost anything...except nightmares. Heather can't stop dreaming about two sisters from centuries ago, twins Prudence and Primrose, who somehow seem tied to her own life. Their presence lurks just beneath the surface of her consciousness, sending ripples through what should be a peaceful summer. The twins might hold the key to putting Heather's soul at rest...or they could slice her future deeper than any knife.