Susannah Cahalan was a healthy young woman who began experiencing severe symptoms like hallucinations. Doctors could not find a physical cause and assumed it was psychological, prescribing her antipsychotics. As her condition worsened, one doctor suggested committing her to a mental institution. However, under pressure from her parents to run more tests, another doctor discovered she had a rare autoimmune disease called Anti-NMDA Receptor Encephalitis attacking her brain. Susannah had been misdiagnosed due to an inability to identify the physical cause of her symptoms.