The story begins in Regensburg, Germany in 1903. There is a rumor at the all-boys Catholic S. Sebastian Music Institute that if someone looks through a window known as The Window of Orpheus in one of the towers and sees a beautiful girl through it, he will fall in love with her. This love will only bring pain for it will end up like the tragic Greek myth of Orpheus and Eurydice.
Two of the students, Klaus and Isaac, see a girl through the window. Not realizing she is a fellow student named Julius, who was raised to be a boy, things spin out of control and their lives are changed forever.