On 27 December 1927, following the opening night performance of his Broadway musical Show Boat, world famous composer Jerome Kern visits the neighborhood where he began his career many years earlier.  As he sits in his chauffeured limousine, Jerome remembers his early days as a young songwriter and the day he arrived at composer James I. Hessler's home seeking professional advice.

While preparing to leave for England to write a symphony, James tells Jerome that he is leaving because he has become disillusioned with the mediocrity of American music.  James dismisses Jerome as one of the many song-writing hacks who come to him for advice until he hears one of Jerome's beautifully composed melodies.  As James's young daughter Sally and Jerome play the song for him, James realizes that his visitor is destined to become a great song-writing success.

The two composers become fast friends, and before James leaves for England, he advises Jerome to "think big" and not waste his time writing frivolous songs.  Jerome takes the advice to heart, but becomes increasingly discouraged by his inability to sell his works.  After concluding that Broadway is no longer hospitable to American composers, Jerome decides to try his luck in Europe and sets sail for England.

Jerome enjoys a happy reunion with James and Sally, who calls Jerome "Uncle Jerry," and the three spend an afternoon at a fair.  There Jerome gets an idea to use swings to go along with a song he has written.  The idea is immediately incorporated into a musical show produced by George Edwards.  Following the show, Charles Frohman, a theatrical producer from New York, asks him to write four songs for his upcoming show in New York.

One day, while riding his bicycle through the English countryside, Jerome meets and falls instantly in love with a young woman named Eva.  A romance between the two flourishes, but Jerome soon finds himself on a ship bound for America, where rehearsals for Frohman's new show are soon to begin.  Jerome's first Broadway show, The Girl from Utah, proves a great success, but while he and James collaborate on a complete score for a new show, Frohman leaves for England to search for new talent.  En route to England, Frohman's ship, the Lusitania, sinks and he perishes.

After receiving encouragement from composer Victor Herbert, Jerome resumes his work and composes one Broadway hit after another.  Jerome eventually returns to England and marries Eva.

Time passes, and Sally, now an aspiring actress, is given her first break in Jerome's new musical Sunny.  However, when the show's producer assigns the title song to Marilyn Miller, Sally deserts both Jerome and her father.  A short time later, James dies of heart disease.  Following the death of his mentor, Jerome loses his will to compose new songs, but his disillusionment soon fades when he finds Sally singing in a nightclub in Memphis.  There Jerome is hired to compose songs for Victor Herbert's next production, Show Boat.  Back in New York, Jerome snaps out of his reverie, and is driven by his chauffeur to a party to celebrate the success of Show Boat.  Jerome's fame eventually takes him to Hollywood, where he is surprised, but pleased, to learn that Sally has been chosen to sing a song that he has written for a motion picture.