Roar of the Crowd: 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.