The song "O Willow Waly" is haunting and creepy all by itself, but it's the stuff of nightmares when superimposed over the horrors at Bly Manor. The storyteller recites its lines, Flora hums it, the music box plays it, and Viola sings it. While it gives off major cursed ancient nursery rhyme vibes, it was actually written by George Auric and Paul Dehn for the 1961 film The Innocents (which is also inspired by The Turn of the Screw).