Ten years ago, Broadway diva Kylie Swanson opened the musical The Haunting of the Opera (a reference to real-life musical The Phantom of the Opera) to a packed audience. That same night, she was murdered backstage by an unknown assailant wearing the mask of the play's villain, Opera Ghost. Years later, Kylie's children Camilla and Buddy have grown into teenagers raised by Roger McCall, a former lover of Kylie's and the producer of a musical theater summer camp on the brink of bankruptcy. When Camilla hears that the camp will be producing a kabuki version of The Haunting of the Opera, she decides that she will sneak into auditions one way or another. She manages to convince a camper overseeing the auditions, Joel Hopton, to let her in and Camilla easily impresses the stage director Artie and wins the lead role of Sofia - much to Buddy's dismay.As the opening day grows closer and closer, Camilla discovers that Artie will only let her perform on opening day as long as she provides him with sexual favors. He emotionally blackmails her by playing her off of Liz Silver, a camper that will do anything to perform on opening night. Camilla tries to ward off Artie's attentions by only making out with him, which disgusts Joel - whom Camilla has largely ignored since the audition. The night before the performance, Artie gives Camilla an ultimatum: either she sleeps with him or he gives the opening night performance to Liz. Camilla initially acquiesces to Artie's overtures, but decides at the last minute that she can't go through with it. After she leaves, Artie is brutally murdered by someone wearing the Opera Ghost mask, but Roger tells everyone that Artie died by accident. Unwilling to potentially lose a visit from important Broadway agent Victor Brady, who is only willing to watch the performance if Camilla is performing, Roger manages to persuade everyone to perform opening night as planned.That night, Joel tries to warn Camilla that Artie was killed and that the murderer is still out there, but his warnings go largely unheeded and the show begins. All seems well with the musical and Victor until later in the performance, when Opera Ghost kills several performers and stops Liz from taking revenge on Camilla for performing on opening night. This causes a gap in the performance, which the cast tries to fill with impromptu music and dancing while Camilla looks for her missing co-star. She instead finds an ever increasing amount of bodies as the murderer kills more and more people.Camilla manages to intervene when she discovers Opera Ghost trying to kill Roger, only to discover that the killer is Buddy, who says that he did it because he did not want Camilla to get involved in the acting world, which he saw as corrupt- especially after he saw Roger kill their mother in a jealous rage. While Buddy is talking, Roger manages to free himself and stab Buddy to death. He chases her throughout the camp and corners her backstage, eventually forcing Camilla to kill him with a buzz saw and stumble onto stage. The audience initially assumes that this was all part of the show and applauds what they believe to be the finale.The film then cuts to the Broadway revival of The Haunting of the Opera with Camilla as the lead. As she prepares backstage, Opera Ghost lunges out of the mirror at Camilla, only for it to be a hallucination.