Charlie Babbitt is a successful car dealer in Los Angeles. When his father leaves most of his inheritance to his long-lost autistic brother Raymond, Charlie is determined to find him and claim what he believes is his. Charlie liberates Raymond from his care facility and sees an opportunity to exploit his brother’s extraordinary savant memory and make a fortune in Las Vegas. But, Raymond's lack of social awareness and rigid routine irritate his brother on the trip. Throughout their trip, Charlie learns more about his brother, autism, and savant syndrome, and what true brotherhood is.