Carlotta thinks she will sabotage the superlatively-talented Christine, but she is really setting herself up to become a target for the Phantom's anger. In Chapter 8, when Erik becomes displeased by Carlotta's emotionless voice, he completely ruins her performance:
No one could have predicted anything like this. Carlotta was still unable to believe what her throat and her ears had told her. The crack of a thunderbolt would not have startled her as much as that hoarse croak springing out of her mouth; and thunder would not have caused her downfall. Whereas a toad crouched on a singer’s tongue will inevitably ruin her. Some have even died from it.
The narrator describes her downfall in dramatic terms, comparing the shock of her voice to that of a thunderbolt. This is an example of dramatic irony because the reader is clued in to expect her downfall even before this scene, but Carlotta continues to believe she will succeed in sabotaging Christine. As the narrator puts it, "no one could have predicted" this course of events; that is, no one in the story could have predicted it. But readers have many context clues throughout the preceding chapters, as well as an intuition about what the music-obsessed Phantom might do to someone who sings poorly yet tries to compete with his beloved Christine.
Erik resents his compulsory mask-wearing, but he is far less masked than the other metaphorically-masked characters. One example of masked feelings includes Christine's bogus engagement to Raoul. In Chapter 12, Christine suggests a "secret marriage" that will last only one month:
"But if we cannot be married, we can become engaged! No one but us will know. There have been plenty of secret marriages! Why not a secret betrothal? Let us become engaged, Raoul, for a month! In a month’s time, you will sail away and the memory of that month will keep me happy for the rest of my days!" She was overjoyed by this prospect. Then she became serious again and added: "This happiness will hurt no one."
Here, Christine claims that the mere memory of their month-long engagement will keep her happy for the rest of her life. Her invention of a bogus union is her attempt to mask the unhappy confusion of being trapped by the Phantom. She and Raoul merely "play" at being husband-and-wife-to-be in a "beautiful game" that serves to cover her sadness for a little while.
Other examples of metaphorical masking include Christine and Raoul's many attempts to deceive Erik and the Persian's lies about why he comes to the opera. By contrast, Erik's mask eventually comes off, leaving him vulnerable to Christine, who receives him with unexpected warmth. This decision to unmask makes Erik the least hidden and most vulnerable character in the book. Masks appear as a significant metaphor for the hiddenness of identity and motive; the irony of Erik's compulsory mask emerges as the other characters' tendencies to mask their true desires or feelings become apparent. Throughout the story, this irony depends on the device of masking as an extended metaphor for concealment.
