Early one morning, Marjorie Lawrence leaves her family sheep farm in Winchelsea, Australia to catch a train and attend an operatic singing competition in Geelong. The next morning, Marjorie's father Bill Lawrence learns from the newspaper she had won the competition. She arrives in Paris on a music scholarship, and is tutored by Mme. Cécile Gilly. Shortly after, Marjorie receives a telegram from her brother Cyril that her father has died. Grief-stricken, Marjorie considers returning home, but Gilly notifies she has selected to play Musetta in a production of La bohème in Monte Carlo. Her debut performance receives acclaim, and she is given a two-year contract.
Marjorie telephones her family of her success, and meets Dr. Thomas King at a hotel. They celebrate with champagne, but Thomas tells her he is to return to the United States to work at a children's hospital after completing his research at the Sorbonne. As Marjorie continues to make successful performances, she appoints Cyril as her business manager, and meets Comte Claude des Vignaux. She is then directed by Leopold Sachse in a production of Richard Wagner's Götterdämmerung at the Metropolitan Opera.
Unbeknownst to her, Thomas attends her performance and they reconnect backstage though Marjorie does not recognize him at first. When she does, Thomas congratulates her and states he now works in obstetrics. Meanwhile, Cyril confronts her sister about not answering Comte Claude's calls. As she is in love with Thomas, Marjorie arrives in his office to resume their romance, though Thomas declines to marry her because of their career paths. When Thomas leaves the hospital, Marjorie tells him she has cancelled her future performances and desires to be his wife. They marry, and Marjorie jeopardizes her career with the Met Opera when she refuses to tour in South America. Thomas insists that she go on tour, but refuses to accompany her so he is not overshadowed by her.
During rehearsals for Tristan und Isolde, Marjorie's voice wavers and she collapses. Thomas flies down, and learns Marjorie has been diagnosed with polio. She recovers the use of her arms and shoulders, and Thomas takes her to Florida to recuperate. Back at home, Thomas plays one of Marjorie's phonographic records to lift her spirits, which prompts her to crawl on the floor to turn it off. Over time, an immobilized Marjorie regains the strength of her voice and soon lands an engagement with the Florida Philharmonic Opera. Backstage, she panics and tries to leave when it is time to perform.
The next morning, Marjorie learns that Thomas has sold his medical equipment and attempts to overdose on prescription pills until Thomas arrives and stops her. Marjorie convinces Thomas to return to New York while she stays behind in Florida. Thomas's friend Ed Ryson invites Marjorie to sing for soldiers at an army hospital, where she performs “Over the Rainbow.” Marjorie is then invited to perform for U.S. soldiers overseas, and returns to the Met Opera which has been accommodated for her disability.
On the opening night, Marjorie performs Tristan und Isolde with the assistance of leg braces underneath her costume. During the performance, Thomas watches her from the stage wing. At the end of the opera, Marjorie receives a thundering ovation.
