After a selfish L.A. yuppie learns his estranged father left a fortune to an autistic-savant brother in Ohio that he didn't know existed, he absconds with his brother and sets out across the country, hoping to gain a larger inheritance.

When car dealer Charlie Babbitt learns that his estranged father has died, he returns home to Cincinnati, where he discovers that he has a savant older brother named Raymond and that his father's $3 million fortune is being left to the mental institution in which Raymond lives.

Motivated by his father's money, Charlie checks Raymond out of the facility in order to return with him to Los Angeles. The brothers' cross-country trip ends up changing both their lives.