Molly McKay, an autistic woman, has spent most of her life in a mental institution after her parents’ deaths in a tragic automobile accident. When budget cuts force the facility to close, she is left in the care of her non-autistic older brother, Buck McKay, who has rarely been involved in her life beyond special occasions as they’ve grown apart.
Buck, an advertising executive who hasn’t settled down, finds his carefree bachelor existence upended by Molly’s exacting routines and needs. She verbalizes very little and tends to arrange her shoes in neat rows, a stickler for order that soon disrupts Buck’s day-to-day existence. His attempts to manage her hygiene and feeding prove challenging, and a daycare option is quickly ruled out as impractical. A cringeworthy moment at Buck’s workplace—Molly marching into a meeting in the nude—highlights how out of sync they are with the outside world and forces Buck to re-evaluate who will look after her. After a chaotic morning, Buck’s assistant agrees to take Molly home, and Buck learns that even small errands can turn into major upheavals when Molly becomes involved in life outside the institution.
A fountain scene, where Molly plays in the water while Buck’s world continues to unravel, marks a turning point: Buck loses his job as a consequence of the incident, and his sense of stability collapses. Feeling restless and isolated, he invites Sam from the institution to visit, hoping for some guidance. Sam, who communicates effectively with Molly, suggests exploring whether Molly might be eligible for a program Buck now works with, a possibility that could help her engage with the broader world.
Molly’s neurologist, Dr. Susan Brookes, proposes an experimental approach: implanting genetically modified brain cells into Molly’s brain. Buck initially resists the idea, but as he witnesses Molly’s capacity for understanding begin to expand in small ways, he finally agrees to proceed. The decision comes with a crisis, however, as Molly experiences a seizure that leaves Buck shaken and worried that she nearly died. When Dr. Brookes pushes for another attempt, Buck’s fear resurfaces, and he hesitates to move forward.
Time passes, and a change starts to take root. Molly shows moments of comprehension and the ability to grasp abstract concepts, prompting Buck to write a simple list of learning goals for her. One morning, Buck wakes to find that Molly has accomplished many of the items on that list. The sight fills him with renewed optimism, and he accompanies Molly back to Dr. Brookes for further development. Under careful guidance, Molly begins a gradual, almost miraculous improvement: she speaks more clearly, engages in conversations, and interacts with others in a way that feels more natural.
With the breakthrough, Buck begins taking Molly to a variety of social experiences—a performance of Romeo and Juliet, a baseball game, and elegant dinners—moments that once felt impossible for both of them. For a time, the improvement seems sustained, and the pair cultivate a relationship that is full of new textures and possibilities. Yet the progress is not permanent. After several months, Molly’s brain starts to reject the transplanted cells, and she slowly slides back toward her earlier state. The hope of a lasting cure gives way to the reality that the improvement can fade, and Buck and Molly must confront the inevitability of regression.
In the final scenes, Buck makes a quiet, heartfelt choice: he accepts Molly’s autism as part of who she is and commits to remaining in her life. He builds a room for her in his own home—a space designed to resemble the one she had at the institution—an enduring symbol of his promise to support her, no matter what changes come. The film closes on a tempered note of kinship and resilience, underscoring a family’s determination to stay connected through the ebbs and flows of Molly’s condition.
