At the beginning of Rain Man, Charlie Babbitt is in the middle of a crisis — he's a high-end car salesman who has lenders breathing down his neck, and Lamborghini deliveries being held up by the EPA. His stress only increases when he learns that his father, who he has been estranged from for years, just died. After traveling to Ohio to settle his will and learning his father bequeathed him a classic 1948 Buick Roadmaster, and nothing else, he then discovers that the rest of his estate was entrusted to a patient at a mental institution. It turns out that this patient is the older brother he never knew he had.
Charlie goes out and meets Raymond, who has autism spectrum disorder (ASD) and an incredible gift for recalling information. Charlie, ultimately, removes his brother from the institution. He tells Raymond's doctor Dr. Bruner (Jerry Molen) he plans to gain custody of him — though it's clear he only wants to do so to claim the estate for himself. His plans are immediately disrupted when Charlie refuses to fly back to Raymond's home in Los Angeles and they have to take the Roadmaster on a cross-country journey.
It doesn't take long for Charlie to realize he's in over his head, where his brother's care is concerned. Raymond is prone to panicking, and becomes frustrated when his strict daily schedule is disrupted. However, Charlie also begins to learn more about his brother, and their unexpected bond creates another huge change in his life.