In what could just as easily be called Obsession, Passion is one of the more unusual entries in Stephen Sondheim's canon. It doesn't have any crowd-pleasing songs to speak of or peculiarly endearing characters (like Sweeney Todd's Mrs. Lovett). It's the story of a withdrawn, terminally ill woman's all-consuming desire for a handsome soldier, and it can be intriguing or tedious, depending on the viewer's temperament. Much of the music is lovely (it won the Tony Award for Best Musical when it played on Broadway), but it's not an easy show to like.
Based on Ettore Scola's 1981 film Passione d'Amore (and Tarchetti's 1869 novel Fosca), Passion opens in 1863 Milan, where Giorgio, a young army captain, is in bed with his lover, Clara, and he has bad news—he's being transferred to a remote outpost and doesn't know when they will be able to see each other again. They make a devoted promise to write each other regularly, continuing their love affair through words.
At his new post, Giorgio is introduced to Colonel Ricci, the commanding officer, and Dr. Tambourri, the regiment's physician. Their conversation is interrupted by a horrifying scream, and Ricci explains that the sound emanates from his cousin, Fosca, who is very ill. The doctor tells him that she suffers from an illness brought on by a mental torment that is manifesting itself physically and will result in her death.
Learning of her love of books, Giorgio offers to lend the doctor some of his for her to read. When she returns them, he's taken aback to meet a feeble and somewhat homely young woman, but her plight brings out feelings of pity in him. She is so starved for affection that she interprets this pity as love. He confesses to her that he already has a lover in Milan, but she scoffs at the authenticity of their affection when he adds that the woman is already married. She continues to develop their romance in her own mind, following him wherever he goes and insisting that the two of them are meant to be together.