Margaret Prior is a socialite who finds escape and purpose as a mentor that brings hope and comfort to the female inmates at Millbank prison. However, she becomes infatuated with Selina Dawes, a medium who was incarcerated after a séance went horribly awry. Margaret, who is at first skeptical of Selina's gifts, soon discovers a world of secrets and shadows, heightened passions, and the allure of the supernatural world.