A grieving upper class woman becomes a "Lady Visitor" at Millbank prison, hoping to escape her troubles and be a guiding figure in the lives of the female prisoners. Of all her friendships with prisoners, she is most fascinated by Selina - a medium.

This psychological mystery/thriller, adapted from Ruth Rendell's novel of the same name, depicts a family on the edge. Two sisters, the elder obsessive Vera, and the younger, manipulative Eden, cut a path of jealousy, murder and revenge that leads to the destruction of their entire family.