One day in 2009, twenty-four-year-old 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 monthlong hospital stay of which she had no memory at all—showed hallucinations, violence, and dangerous instability. Only weeks earlier, Susannah had been ...