<P> Susannah Cahalan (Moretz) is a New York Post writer, who works with her boss Richard (Perry) and desk neighbor / co-worker Margo (Slate). She meets a sound producer named Stephen (Mann) and they become friends . Susannah begins to experience strange things (such as being in a trance state, seeing people--who are not actually present--who talk about her, and hypersensitiveness to annoying noises and tactile sensations). Susannah's behavior becomes unusually erratic . After several days of mishaps made by her in the office due to her altered behavior, including talking to Stephen while under her desk, as well as insulting a Senator, his public relations person and firm, Susannah suffers a seizure and seeks treatment . </P> <P> After consulting with a clinic, her father Tom (Armitage) confronts Stephen about not calling her parents regarding the incident . Tom suggests that she stay with her parents, which Susannah refuses to do, but in the end she leaves to stay with her mother and stepfather . At her mother's house, Susannah has another seizure . She is taken to a clinic where Susannah undergoes an MRI . The doctor advises her mother, Rhona (Moss), that Susannah has been partying too much, working too hard and not getting enough sleep . While at one of her doctor's appointments, Susannah expresses she has bipolar disorder, since she is creative and "creative people are bipolar". Another doctor prescribes an anti-psychotic medication which, after reading of their side effects and believing them as causing her symptoms, she refuses . Rhona gets her to take the pills anyway, and asks her father to watch her because she is too difficult to handle . During dinner with her father, she becomes violent, yelling at her father to stay away . Her parents demand that she is hospitalized despite MRI, EEG and physical tests all showing normal results . </P> <P> One of the doctors says to her parents that she is possibly suffering from schizophrenia . The doctor tells them that if Susannah's behavior does not improve, she will be transferred to another hospital, where they can deal with psychological problems . Susannah becomes catatonic, and Dr. Souhel Najjar is asked to help in investigating her case . Najjar has Susannah draw a clock . She draws it with all of the numbers (1--12) on the right side of the clock, leading the doctor to believe that the right hemisphere of her brain is swollen and inflamed . Najjar has her undergo a brain biopsy in order to take cells from her brain for diagnosis . It is found that Susannah has anti-NMDA receptor encephalitis and Najjar describes it to her parents and Stephen as her "brain is on fire". Dr. Najjar prescribes her a treatment, which leads to a slow, but full recovery of her cognitive abilities . </P> <P> Seven months later, Susannah is back at work and presents her first written piece to Richard since her recovery . A grateful Richard tells her to start writing a book about her experience . Sitting at her desk, she begins to write the story, entitled Brain on Fire . </P>

What is the disorder in the movie brain on fire