Based on author Ruth Rendell's novel of the same name, A Dark Adapted Eye follows the jealous and arguably insane path of the domineering Vera Hillyard (Celia Imrie), whose obsessive need to control her sons (the older is prone to demonstrating decidedly aggressive behavior, the younger may or may not be legitimate) and daughter plays a prominent role in her own undoing. Meanwhile, her manipulative sister, Eden (Sophie Ward), ultimately provokes Vera into what the community believes to be the deliberate murder of a child.