The highly fictionalized story of Nellie Melba, Australian-born soporano who rose to operatic fame in the latter part of the 19th century and who had a desert and form of dry toast (true) named after her. In her film debut, the Metropolitan opera's Patrice Munsel, plays the title role in a film that primarily strings together eight excerts from well-known operas as well as one or two lighter numbers and a montage of famous opera personalities featuring the chorus of the Covent Garden Opera and members of the Sadler Wells Ballet. The story follows the career of Melba from the time she left her father's Australian cattle ranch and a suitor to travel to Paris to get her voice training, and picks up another suitor. She debuts in Brussells and is a smash hit followed by international fame. The suitor from Australia shows up in Monte Carlo, marries her and soon is cast in the role of "Mr. Melba" until he can take it no longer and returns to Australia, while Melba decides her voice belongs to the world and sadly goes on alone.

In the late 1890s, famous opera singer Nellie Melba is invited to sing for Queen Victoria at Windsor Castle, and her first song selection, "Comin' Thro' the Rye," evokes memories of her upbringing on a cattle ranch near Melbourne, Australia: Thomas Mitchell, Nellie's father, has arranged for her to study singing in Paris, and on the day she leaves, prayers for her happiness and success are said at the small church where she has been a soloist. Later, at the railway station, her sweetheart, Charles Armstrong, is very upset that she is deserting him. In Paris, after a mixup at her lodgings, where she is suspected of being a lady of the evening, Nellie meets Englishman Eric Walton, a young man-about-town, who invites her to dine with him. At the restaurant, Nellie sings an operatic aria for the customers, and Eric realizes that she could become a great singer and suggests she study with the legendary vocal coach Madame Mathilde Marchesi. Although Marchesi has retired and is under doctor's orders, Eric arranges to have Nellie push her bathchair during an excursion in a park and, ultimately, Nellie is able to audition for her. Despite her illness, Marchesi decides to coach Nellie, and they begin a very intense, very strict, series of lessons. One day Eric visits Marchesi's home along with Paul Brotha, director of the Brussels Opera, who listens, unannounced, as Nellie sings. Brotha wants to engage her for a performance in his theater, but as Marchesi will not permit Nellie to sing in public yet, Brotha and Nellie devise a scheme whereby she will sing for one night, then return to Paris, without Marchesi finding out. They select a stage name of Melba, derived from Melbourne, and Nellie debuts as "Gilda" in Rigoletto and is well received. Upon her return to Paris, Marchesi drills her with endless vocal scales, then reveals that she knows about her debut and is very happy for her. Marchesi then arranges for her to perform in Lucia di Lammermoor at the famous Covent Garden Opera House in London. Cesar Carlton, patrician owner of the London hotel where she is staying, welcomes Nellie and takes her to the Opera House, then leaves her on the empty stage. As she stands where all the great singers have stood, she imagines them performing: Giulia Grisi, Jean Lassalle, Charles Santley, Adelina Patti and dancer Taglioni. Later, Cesar tells her that he will be giving a party in her honor after her opening performance. However, in the excitement of her highly successful debut, she forgets about Cesar's party and goes to dinner with Eric. Cesar is furious with her as half of London was waiting for her at the party, but finally forgives her and kisses her. After appearances in Paris, Nellie performs in Monte Carlo and enjoys the attentions of both Eric and Cesar. Eric arranges for her to meet American impresario Oscar Hammerstein, who invites her to join his Manhattan Opera company, with which he is trying to break the Metropolitan's monopoly. However Charles, Nellie's former sweetheart and now a very successful cattle rancher, surprises her in Monte Carlo and sweeps her off her feet. They marry immediately, and on their honeymoon, Charles attempts to manage his interests in Australia while coming to grips with the demands of his wife's career. After performances in Milan and St. Petersburg, they return to Monte Carlo, where Hammerstein tells Charles that Nellie has rejected his contract and intends to abandon her career to return to Australia. Hammerstein asks Charles' permission to try to persuade her to continue to sing. However, in London, Charles becomes upset by reporters who regard him as "Mr. Melba," and although Nellie learns that Charles intends to return to Australia, Hammerstein convinces her that she must continue her career. After she and Charles amicably toast her upcoming conquest of New York, a heartbroken Nellie lets him depart. Nellie then leaves for Covent Garden and a performance of Roméo et Juliette . Back at Windsor Castle, Queen Victoria tells Nellie how much she enjoyed listening to music with her late husband and how difficult it is to carry on when only loneliness remains, but adds that there are greater obligations than to oneself. Nellie understands what the Queen is saying and sings again for her.