The first trailer for The Haunting of Bly Manor, unsurprisingly, didn't give away many specifics about the show or its spooky twists. But the eerie song playing in the background of
that ambiguous teaser was, as it turns out, telling us a lot more about the show than we could've ever realized at the time. "O Willow Waly," the song in question, is a significant choice for a couple of reasons, so here's a quick primer.
The song "O Willow Waly"—written by George Auric and Paul Dehn—was originally created for the 1961 film The Innocents. This is meaningful because The Innocents is perhaps the most famous screen adaptation of Henry James's novella The Turn of the Screw, which is also the source material for The Haunting of Bly Manor. A psychological horror film directed by Jack Clayton, The Innocents follows a young governess in charge of two orphans and becomes convinced their country estate is haunted. Bly Manor follows that same loose outline, though it also incorporates several of James's other novellas and short stories.
"O Willow Waly" is memorably played on a music box during The Innocents, but in Bly Manor it recurs in several different scenes throughout the season. The lyrics to the song are the very first words we hear in the show, as Carla Gugino's mysterious narrator recites them in a voiceover. Let's take a look at the lyrics:
We lay my love and I beneath the weeping willow
But now alone I lie and weep beside the treeSinging "Oh willow waly" by the tree that weeps with me
Singing "Oh willow waly" till my lover return to meWe lay my love and I beneath the weeping willow
A broken heart have I. Oh willow I die, oh willow I die
The full significance of the song, and its mournful lyrics about a lost lover, won't become clear until the finale. But it recurs throughout the show, mainly in subtle ways. it's sung, whistled, and hummed by Miles, Flora, and Peter Quint in different scenes. Initially, the obvious explanation is that the song is meant to echo Rebecca Jessel, the children's former governess who seemingly dies by suicide after being abandoned by her lover, Quint.
But once Gugino's narrator is revealed to be an older version of Jamie—whose romance with the show's protagonist, Dani, becomes central to the series—the song takes on an even clearer meaning. To save Flora and Miles from being permanently possessed by the ghosts of Bly Manor, Dani confronts the manor's most fearsome ghost of all, Viola, aka the Lady in the Lake. Dani invites Viola into herself to spare the children, and Viola accepts, becoming a part of Dani.
Dani and Jamie are able to leave Bly and start a life together, while the Wingrave family move overseas. But Dani is never the same again. She feels the burden of Viola's presence constantly, and feels a sense of impending doom that she can never fully shake. She knows, instinctively, that sooner or later she will be consumed by Viola's darkness, but with Jamie's support she's able to stave it off and enjoy at least a decade of happiness.
Finally, after she realizes Viola is becoming a threat to Jamie, Dani returns to Bly Manor and drowns herself in the haunted lake, where she takes over from Viola as the new Lady in the Lake. Unlike Viola, she's a benign spirit, and never harms anyone—but like Viola, her memories fade over time, and so she has no memory of her life with Jamie. The reality of who Dani was only lives on "in the memory of the woman who loved her most."
So… that's devastating. And by the end of the finale, it's very clear why Jamie opens her voiceover with the lyrics to "O Willow Waly," which perfectly describe her life without Dani.