In "Passion," Stephen Sondheim had no intention of writing a conventional love story. He makes this clear in the opening scene, where he puts into the mouths of his two beautiful lovers, Clara and Giorgio, some of the most purposely banal lyrics he ever wrote, making it clear that these lovers are not the interesting ones in this story.

Where the composer wants to direct our attention is toward Fosca, the sickly wedge that slowly splits apart that conventional pair. Fosca literally believes all of the romantic cliches about love that others, including Clara and Giorgio, merely spout. The notions of an all-consuming devotion, an inability to live without the beloved, a loss of all perspective, are realities to her. Taking their cue from Iginio Ugo Tarchetti's 1869 novel "Fosca" and Ettoré Scola's 1981 film "Passione d'Amore," Sondheim and Lapine have made Fosca painfully plain, an insurmountable defect for a woman in 1863 Italy, where the only options are to be "a daughter or a wife." In the 1994 New York production, which won the Tony Award for best musical, Fosca (played by Donna Murphy) was considerably more than physically plain. She was downright unpleasant: irrational, obsessive, unrelenting. She so thoroughly embodied her monomania that she called into question all of our comfortable ideas about love and lust, kindness and cruelty.

Passion is essentially an exercise in opposites, primarily in the contrast between Clara and Fosca. Contrast has been a regular device in the muscials for years, but never had the contrast been so clear, or quite so much the point of the story. The original novel is structurally schematic - Clara means "light" whereas Fosca means "dark" - but Sondheim has emphasised the differences between these two women by giving them their own musical languages. Sondheim and Lapine have used this contract to explore the theme of love and relationships in a way that echoes Sondheim's earlier work in Company, Follies and A Little Night Music. But this story is also about light and dark, the physical and the spiritual, the head and the heart.