James Stewart stars in this biopic of American bandleader Glenn Miller. A talented young trombonist, Miller (Stewart) falls for Helen Burger (June Allyson) while studying at the University of Colorado. He gets his first big break after leaving college performing his own arrangement of 'Everybody Loves My Baby' at an audition, and builds himself a reputation working for bandleader Ben Pollack (playing himself). Marriage to Helen follows, and Miller finds success with his own 'sound' after a trumpet player splits his lip, forcing him to substitute a clarinet solo on 'Moonlight Serenade'. He goes on to become the leading jazz bandleader of his day, but tragedy looms with the outbreak of World War Two.