An acid-scarred composer rises from the Paris sewers to boost his favorite opera understudy's career.
Pit violinist Claudin hopelessly loves rising operatic soprano Christine Dubois (as do baritone Anatole and police inspector Raoul) and secretly aids her career. But Claudin loses both his touch and his job, murders a rascally music publisher in a fit of madness, and has his face etched with acid. Soon, mysterious crimes plague the Paris Opera House, blamed on a legendary "phantom" whom none can find in the mazes and catacombs. But both of Christine's lovers have plans to ferret him out.—Rod Crawford <[email protected]>
After a performance of Martha at the Paris Opera House, police inspector Raoul Daubert (Edgar Barrier) proclaims his undying love to singer Christine DuBois (Susanna Foster), despite her known affections for both her career and baritone Anatole Garron (Nelson Eddy). The conductor Villeneuve (Frank Puglia) then tells Christine that she has great promise, but must choose between the opera and "a normal life." The news is not so fortunate for violinist Erique Claudin (Claude Rains), who is fired after 20 years in the opera's orchestra. Returning home, he is threatened with eviction by his landlady, who questions his confessed poverty.
The next day, Claudin visits singing instructor Signor Ferretti (Leo Carrrillo), whom he has been secretly paying for three years to coach Christine. With no funds to continue the lessons, Claudin offers his new concerto to music publishers Pleyel and Desjardines. Later, after mistakenly believing that the music publisher has stolen his work, Claudin strangles Pleyel to death, then is facially disfigured when the publisher's assistant throws a tray of acid in his face. The violinist escapes into the sewers of Paris, and the next day, the master key of the opera house is stolen, as well as a costume and two masks.
Meanwhile, as Christine sings Anatole a childhood lullaby, Raoul arrives to question her about the murderer, as a bust of her was found in Claudin's apartment. At a performance of Amour et Gloire, Christine hears Claudin's disembodied voice, telling her that, with his help, she is going to be a great singer. The mad violinist then drugs soprano Biancarolli's (Jane Farrar) drink, and understudy Christine takes her place with great success. Biancarolli accuses Garron of drugging her and demands a police investigation. She agrees to drop all charges if Christine is returned to the chorus and no mention of her magnificent performance is published.
Later, Claudin visits Biancarolli, ordering her to leave Paris, and when she refuses, murders the singer and her maid. The opera is closed by the police, only to have a note arrive, demanding Christine's performance. After Raoul agrees to re-open the opera, but with another singer, Lorenzi, in her place, to lure the murderer out, Christine is visited by her two suitors, who argue over their two plans to catch the killer. Anatole convinces Franz Liszt to perform Claudin's concerto as another lure and the opera house re-opens with Le prince masque de Caucasie.
A new note from the "Phantom" is found, threatening harm if Lorenzi performs in Christine's place. To gain access to the performers, Claudin kills an undercover policeman, taking his place backstage, and sends a giant chandelier crashing down on the audience when Lorenzi begins to sing. He then abducts Christine and takes her into the catacombs of the opera house. He tells her that she can sing now, but only for him.
Upstairs, Anatole instructs Liszt to play Claudin's concerto, as he and Raoul search for the missing singer. Claudin accompanies the famous pianist, and Christine slowly recognizes the piece as her childhood lullaby. The two suitors follow the music of Claudin's piano and Christine's singing to find the Phantom and his captive. Just as Christine removes Claudin's mask and discovers his disfigured face, her rescuers arrive. Raoul attempts to shoot the advancing madman, but Anatole deflects his arm, sending the bullet into the ceiling and causing the collapse of the Phantom's lair. Anatole, Christine and Raoul escape the disintegrating walls, but Claudin is buried alive. Christine questions how Claudin composed the concerto around her lullaby, but Anatole tells her that she and Claudin were from the same part of France, and that it must be an old folk song of the area. As she utters sympathetic words about her patron, Anatole comforts her, stating that Claudin's madness will soon be forgotten, but his concerto will live forever.
Later, after a triumphant performance, Christine is congratulated by her two suitors. They demand that she choose between them, but she elects instead to greet her adoring public. Realizing that she has made her choice, the baritone and the detective decide to dine together.
