Insomnia tells the story of successful career woman Emma Averill, who fears she is losing her mind after suffering from sleep deprivation two weeks before turning 40. Her mother had a similar experience at the same age, suffering a violent psychotic breakdown on the night of her 40th birthday. But even as she relives the experience of her mother, Averill believes other forces may be at work. Her mother is hospitalized with a sudden injury, her estranged sister returns without warning, and she feels as if she is being watched. Only by investigating the truth of her painful past, can she find the answers to her present.