Johnny Tracy son of veteran race driver Pop Tracy is working his way up on the racing circuit but is urged by his sweetheart Marcy Parker to give up the track if he wants to marry her He persuades her to marry him on the promise that he will quit after racing once in the Indianapolis 500 but he is injured in a qualifying race and goes to work as a spark plug salesman for Mackey an old family friend He is a failure at selling but Marcy changes her attitude towards his racing and he qualifies for the 500