A little boy named Jimmy Murphy lost his mother in the Great San Francisco Earthquake. He goes to live with relatives who eventually give him a motorcycle. Just before graduating from school he quits and opens a motorcycle repair shop. Later, he starts working for the Duesenberg factory racing team as a mechanic, then a riding mechanic, and then a driver. What a driver he becomes! He wins the Indianapolis 500, becomes the first American to win a Grand Prix race, and claims two national driving championships in the United States. This is his story.