"The Phantom of the Opera," a novel by French writer Gaston Leroux and a famous 1986 musical, is a story about a mysterious, disfigured man who chooses a protégée, Christine Daae, to sing his works and become first lady of the stage in a Parisian opera house. The story unfolds as Raoul, a new patron of the opera house, and the Phantom battle for Christine's love.
"The Phantom of the Opera" takes place in 1881, when the disfigured phantom chooses Christine Daae, an orphaned dancer at a Parisian opera house, to become his protégée. Christine believes that the phantom is the Angel of Music, a figure that her father promised would protect her when he died. The Phantom teaches her to sing his works, but on the eve of her debut, the new patron of the opera house recognizes Christine as an old childhood friend. Raoul, handsome and rich, is smitten with Christine and pursues her despite the Phantom's ominous warnings.
At the end of "The Phantom of the Opera," the Phantom kidnaps Christine and forces her to promise marriage to him; if she refueses, he vows to blow up the opera house. She agrees to save both Raoul and innocent lives, and after the Phantom kisses her on the forehead, she returns his kiss. Overcome by emotion, as he has never been kissed or allowed to kiss, the Phantom shows her true love and sets her free--ultimately to be with Raoul.
According to About.com, the plot of "The Phantom of the Opera" is about the obsessive pursuit of something--love, money, revenge, status, etc.--and the redeeming qualities of love; in this case, both for the Phantom and Christine.