The story begins with a PROLOGUE, set in Paris, 1911. An auction is being held on the stage of the Paris Opera House. One man seems to be buying many sentimentally valued items - including a musical box with the figure of a mechanical monkey. This man is Raoul, Vicomte de Chagny. The next item is a reconstructed chandelier, which featured in the 'famed tragedy of the Paris Opera'. The auctioneer calls for a demonstration of the new wiring, and suddenly the chandelier rises to the ceiling of the theatre, transporting the audience back in time... (OVERTURE).
ACT I - Paris, 1881: The company is rehearsing a new opera, Hannibal. The manager of the Opera arrives and announces his retirement. The new managers, Andre and Firmin are introduced. Andre asks Carlotta, the company's Prima Donna, to perform a piece from the opera for them. As she is singing, a backdrop falls suddenly, almost killing her. Buquet, the chief flyman, is called but he can offer no explanation. The ballet girls whisper that it must be the work of the "opera ghost". Carlotta is furious and storms out, vowing not to return until these strange occurrences stop happening. The new managers, who are now left without a leading lady, have their problems added to when Madame Giry, the ballet mistress, hands them a note from the opera ghost, in which he demands a salary and the use of Box Five for the opera. Meg Giry, Madame Giry's daughter, suggests that her friend Christine Daae could take Carlotta's place. Christine has been taking singing lessons, but claims she does not know from whom.At Madame Giry's insistence the managers grant her an audition (THINK OF ME). As Raoul watches from the managers' box and applauds her performance, he is echoed by an unseen voice.
Meg asks Christine about her teacher, but all Christine can tell her that it is the "ANGEL OF MUSIC" which her late father had promised he would send to her. She has only heard him in her dressing room; she has never seen him. Raoul goes backstage to her dressing room to congratulate Christine. They realize that they were playmates as children (LITTLE LOTTE). Raoul insists on taking her out to dinner and leaves to get his coat. As soon as he is gone, the strange voice is heard again, and gradually a figure appears behind the mirror. It is the Phantom, her ANGEL OF MUSIC. The mirror glides open and THE PHANTOM OF THE OPERA draws Christine inside with him. Raoul returns and hears the voice, but the door is locked. Suddenly the dressing room door opens, but when Raoul enters the room, the mirror has slid shut and it is empty.
Christine and the Phantom journey through the labyrinth beneath the Opera House, crossing a lake to arrive at the Phantom's lair. The Phantom explains why he has been teaching Christine - so that she may sing his MUSIC OF THE NIGHT. Christine falls into a trance and wakes the next morning to the sound of a musical box (I REMEMBER). The Phantom is seated at his organ, absorbed in his composition. Christine quietly approaches him and unmasks his from behind. Furious, he turns on her, and Christine recoils from the horror of his face and his anger (STRANGER THAN YOU DREAMT IT). Once his anger is spent, he breaks down, and Christine, moved by pity, returns his mask. He takes her back to the surface.
Buquet catches sight of the pair as they return. Madame Giry also witnesses the scene, and cautions Buquet not to speak of what he has seen (MAGICAL LASSO). There is confusion everywhere surrounding Christine's sudden disappearance. Raoul, Carlotta, Piangi, Madame Giry and Meg all meet in the managers' offices, brandishing NOTES from the Phantom. The letter that causes the most debate is that which demands that Carlotta be replaced by Christine in the lead role of the upcoming opera Il Muto. The managers reassure Carlotta that she will remain the star and that Christine will be cast in a silent role. The Phantom's voice is heard warning them against that course of action (PRIMA DONNA).
For the performance, Raoul sits in Box Five. The Phantom interrupts the show, repeating his demands, and when these are still ignored, he magically causes Carlotta to croak like a toad instead of singing (POOR FOOL, HE MAKES ME LAUGH). The managers give in to the Phantom and offer a ballet sequence while Christine changes for the performance. During the ballet Buquet's body, hung with the Punjab lasso, falls from the flies. In the ensuing panic, Christine and Raoul flee to the roof. There she tells him of her experiences with the Phantom (WHY HAVE YOU BROUGHT ME HERE?). Raoul is incredulous, but offers her protection. They profess their love for each other, and agree to leave together that night (ALL I ASK OF YOU). Once they leave, the Phantom emerges from where he has been listening and vows revenge. As the cast of Il Muto are taking their bows, he brings down the chandelier, which lands at Christine's feet on the stage.
ACT II - Paris, 6 months later: The Opera is having a MASQUERADE to celebrate the New Year. The Ensemble activity becomes background, as Andre, Firmin, Meg, Giry, Piangi and Carlotta come to the fore, glasses in hand. They clink glasses and move off as Raoul and Christine emerge. She is admiring a new acquisition: an engagement ring from Raoul, which she has attached to a gold chain around her neck. Christine, almost coquettish, almost jittery, goes from man to man. But too many of her partners seem to be replicas of the Phantom, and each spins her with increasing force. Eventually Raoul rescues her and holds her tightly. He whirls her back into the dance, as the music heads towards its climax. A figure dressed as Red Death appears on the staircase. It is the Phantom. He gives the score of his opera to Andre, demanding that is be performed (WHY SO SILENT). He tears the engagement ring from Christine's neck and disappears. Raoul questions Madame Giry about the Phantom, and she tells him what she knows - that he is a deformed genius who escaped from a freak show, and was presumed dead, but that he still lives somewhere in the Opera House. Andre and Firmin have no wish to perform the Phantom's work (NOTES II). However, Raoul proposes a plan, in which they go along with his plans, and then, when he attends the performance, they will be prepared. Christine does not want to become involved, but eventually agrees (TWISTED EVERY WAY). The frustrated company begins rehearsals.
Christine goes to visit her father's grave (WISHING YOU WERE SOMEHOW HERE AGAIN). While there, the Phantom appears and attempts to regain his influence over her (WANDERING CHILD). However, Raoul arrives and takes Christine away. The Phantom is furious and declares war on them both (BRAVO, MONSIEUR).
The performance of Don Juan Triumphant, the Phantom's opera, begins. Police officers have secured all the doors. As the opera progresses, it becomes obvious that Piangi has been replaced by another singer (THE POINT OF NO RETURN). Christine unmasks the Phantom in front of the audience. Police rush onto the stage, but the Phantom is able to take Christine and escape. Piangi, who has also met with the Punjab lasso, is discovered behind the scenes. Raoul follows the Phantom, aided by Madame Giry (DOWN ONCE MORE). She shows him the way to the lake. They are followed by an angry mob - TRACK DOWN THIS MURDERER. In the Phantom's lair, Christine confronts the Phantom with the fact that his true disfigurement is in his soul. Raoul arrives, and the Phantom lets him in, only to trap him in a noose and offer Christine an ultimatum: either she stays with him or Raoul dies. Christine's answer is to kiss him. Stunned by this act, the Phantom lets them both go. Christine comes back to return his ring, and he tells her he loves her. She leaves with Raoul in the boat. As the mob draws in to the lair, the Phantom sits in his throne, drawing his cloak around him. Meg is the first to arrive. She approaches the throne and tears the cloak away. All that is left is the Phantom's mask.