Grace Marks has been convicted for her involvement in the vicious murders of her employer, Thomas Kinnear, and Nancy Montgomery, his housekeeper and mistress. Some believe Grace is innocent; others think her evil or insane. Now serving a life sentence, Grace claims to have no memory of the murders.

Dr. Simon Jordan, an up-and-coming expert in the burgeoning field of mental illness, is engaged by a group of reformers and spiritualists who seek a pardon for Grace. He listens to her story while bringing her closer and closer to the day she cannot remember. What will he find in attempting to unlock her memories? Is Grace a female fiend? A bloodthirsty femme fatale? Or is she the victim of circumstances?