One day in 2009, journalist Susannah Cahalan woke up alone in a strange hospital room, strapped to her bed, under guard, and unable to move or speak. A wristband marked her as a "flight risk," and her medical records—chronicling a month-long hospital stay of which she had no memory at all—showed hallucinations, violence, and dangerous instability. In this powerful, fast-moving narrative, Susannah tells the astonishing story of her inexplicable descent into madness and the brilliant, lifesaving diagnosis by renowned neurologist Souhel Najjar, who suspected a newly classified autoimmune disorder, possibly tied to schizophrenia and autism, in which the body attacks the brain.