In the mysterious Paris of the 19th century, the Opera House is famous for its great plays and shows.
However, no one imagines that behind that place where everyone lives magical moments, hides a ghost so terrifying that the fifth box of the theater is forbidden to all the cast. "F", a ghost whom everyone fears, lives surrounded by rumors about his existence. However... not everyone believes in it. Christina Dae, a chorus girl with a voice like no other, refuses to consider that such a thing could exist, even though a part of her thinks that not everything said about "F" is real. Therefore, Christina is not afraid to go to practice and walk where no one else does. What if those rumors about that mysterious ghost were real?