The central character is a middle-aged woman named Emma Averill, who is afraid of losing her sanity. For a long time, the main protagonist suffered from insomnia. She couldn't sleep for two weeks leading up to her 40th birthday. Emma's mother had a similar experience at the same age: on the night of her 40th birthday, she had a severe breakdown. But even as she relives her mother's experience, Averill is convinced that other forces may be at play.