The original Sibelius did write an opera called "The Maiden in the Tower" - not your standard Sibelius either: "the lustful Bailiff (baritone) has seized the virginal Maiden (soprano), and imprisoned her in the castle tower. The noble retainers think the worst, and disown her, but the Lover (tenor) still believes in her innocence. He comes to rescue her, and draws his sword against the Bailiff..."

Nothing in it about things under the floorboards, so far as I know.