When a comatose woman suddenly wakes up and starts painting scenes she's never witnessed, with a skill she's never had, medical science has no explanation. As more bizarre phenomena manifest, including strange voices coming from her mouth, even her doctors wonder whether the woman may be possessed.

Frustrated and frightened, the patient's sister turns to Harper to discover who--or what--is occupying her sister's body. As Harper digs into the case, she discovers other patients struck with the same mystifying afflictions and a disturbing connection to one of the most gruesome episodes in Washington's history....