Martie Rhodes, a happily married video games designer takes an agoraphobic friend to therapy sessions twice a week. Each trip is a grim ordeal but the experience has brought the two friends closer together. Then one morning, Martie experiences a brief, irrational but disquieting fear of – her shadow. When autophobia – one of the rarest and most intriguing phobias known to psychology – is diagnosed, suddenly, her life radically changes. Her husband Dusty loves her deeply and is desperate to discover the cause of the autophobia. But as he comes closer to the truth, Dusty begins to show signs of a psychological disorder even more frightening of that afflicting Martie.