"A 28-year-old autistic woman named Molly McKay has lived in a mental institution from a young age following her parents' deaths in an automobile accident. When the institution must close on account of budget cuts, Molly is left in the care of her non-autistic older brother, Buck McKay, an advertising executive and perennial bachelor. Molly, who verbalizes very little and is obsessed with lining up her shoes in neat rows, throws Buck's life into a tailspin as she runs away from her nurses and barges into a meeting at Buck's agency naked.
Molly's neurologist, Susan Brookes, suggests an experimental surgery in which genetically modified brain cells are implanted into Molly's brain. While Buck initially balks at the suggestion, he finally consents to the surgery and Molly makes a gradual but miraculous recovery, speaking fluidly and interacting with others in a normal way. Buck begins taking Molly to social events, like a production of Romeo and Juliet, a baseball game and fancy dinners. However, after a few months, Molly's brain begins to reject the transplanted cells and she begins to regress into her previous state. Both Molly and Buck must accept the eventual loss of Molly's cure and her regression into her previous state.
In the final scene of the film, Buck accepts Molly's autism and vows to remain in Molly's life by creating a room for her at his home that looks just like the room she had at the institution."

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