At a small town May Day celebration, elderly Miss Morrison (Jeanette MacDonald) tries to console her young friend Kip (Tom Brown), whose sweetheart Barbara (Lynne Carver) has been offered a job on the operatic stage.

Later, Barbara goes for comfort to Miss Morrison, who reveals that years ago she was the internationally famous opera diva Marcia Mornay.

Miss Morrison then relates her story: Marcia, a young American singer in Paris, is guided to success by famed but stern voice teacher Nicolai Nazaroff (John Barrymore), who introduces her at the court of Louis Napoleon.

Paul then steals tickets to see her perform in the opera Les Huguenots that evening, and after he is thrown out of his seat by the manager, he goes to her dressing room and only leaves when she promises to join him at St.

In New York, Nicolai arranges for Marcia to sing 'Czaritza' (a fictional opera with music from Tchaikovsky's Symphony Number 5), co-starring Paul, who has become a baritone of some note.

At rehearsal, they act at first as if they never have met, but Nicolai begins to suspect the truth when Archipenco (Herman Bing), Paul's singing teacher, talks about meeting Marcia in Paris many years earlier.

On a brilliant opening night, Nicolai becomes jealous over the obvious emotion in Paul and Marcia's onstage love scenes, but doesn't know that they plan to run away together.