The managers of the Paris Opéra learn the 'ghost' is real: a salary is demanded, Box Five must be left empty, and a stagehand named Joseph Buquet is found hanged. Christine Daaé's voice has become extraordinary overnight. Raoul de Chagny attends her triumphant gala performance and hears a man's voice from behind her dressing-room mirror.

Christine confides to Raoul that her teacher is the Angel of Music her dead father promised to send. Raoul overhears Christine's lesson from behind her mirror and becomes convinced she has a secret lover. Erik reveals himself and takes Christine through the mirror to his underground domain for the first time. She sees his face — and his face destroys everything.

Christine and Raoul secretly fall in love and become engaged on the roof of the Opera. Erik discovers the engagement by eavesdropping. The Persian — a mysterious man connected to Erik's past in Persia — appears. Erik sabotages the production of 'Faust,' causes catastrophic accidents, and sends Christine increasingly desperate and threatening letters.

On the night of Christine's greatest performance as Marguerite in 'Faust,' Erik abducts her through the mirror during the curtain call. The managers, Raoul, and the Persian discover she has vanished. Raoul's brother Philippe — who disapproves of the engagement — complicates the rescue mission. The Persian agrees to guide Raoul into the Opera's underground.

Raoul and the Persian descend through hidden passages, are captured, and are locked in Erik's mirrored torture chamber — a room designed to simulate a forest in the tropics that drives prisoners to madness and heat exhaustion. Erik gives Christine his ultimatum: marry him, or he will detonate the gunpowder under the Opera and kill everyone at the performance above.

Christine agrees to remain with Erik permanently in exchange for Raoul's life. She gives Erik a compassionate kiss on his forehead — not from fear or manipulation, but from genuine feeling. Erik, broken open by this first freely given tenderness, cannot proceed with his plan. He releases Raoul and the Persian. He sends Christine away.

Christine and Raoul flee. Erik retreats underground and dies alone within days of releasing them. The Persian reports to the narrator. Erik's body is later found in the cellars — still wearing Christine's ring on his finger. The novel closes with the narrator locating the skeleton and confirming the documentary evidence.

Leroux's narrator assembles the evidence that Erik was a real historical figure: architect, magician, musician, murderer, and the most unhappy man who ever lived. Final reflections on what the Opera Ghost was and what his story means.