Young American doctor Simon Jordan arrives at Canada's Kingston Penitentiary to study the perplexing mind of Grace Marks, a convicted murderer.
Grace shares a palm reader's grim predictions for her future and recounts the fate of her friend, Mary Whitney, a girl who was full of life.
Grace wrestles with a terrible secret. Soon after, she meets Nancy Montgomery, a pretty housekeeper who will change the course of her life.
Dr. Jordan digs deeper into Grace's memories to learn more about James McDermott, a hot-tempered handyman whose confession helped convict her.
Grace recalls the day of the murders in more detail just as a familiar face from her past threatens to undo everything Dr. Jordan has been working for.
After talking with Grace's lawyer in Toronto, a doubtful Dr. Jordan returns to Kingston to observe Dr. DuPont's unorthodox "experiment."