I am fascinated by this movie! I think I get it. (spoilers)
I don't normally get this way, but I have gotten fascinated by this movie and have watched it three times. I just didn't get it, or big parts of it, and I thought there was something there that I was supposed to get.
I think I got it after the third time watching it. I think. At least big parts of it.
Lily is narrating. She is in ghost form when she narrates. Saying the pretty thing you're looking at, I am SURE is me.
She says that because in the intro she lays out the meaning of the movie in her ghost narration: she says that people stay in the place where they died because they wander the floors in a confused state, looking and straining to see...their death. Tending to the floors and their bodies as they would a withered garden. They can't remember their last moments, and even when they see it, it's like looking at a face behind a wet window, all blurry. They can't make it out. The ghosts are free to go, but they stay so they can see themselves and their last moments. THAT IS HOW THEY ROT. That is how they rot, instead of moving on. As Iris says, "you pretty things rot in place and fall apart like flowers, with only yourselves to look at."
Why the closeup of Lily holding the key to the house with the label "Lily" in the beginning? Because that's how Lily the ghost knows that is herself...she says in that scene the line about the pretty thing you're looking at is, I am SURE, me.
Polly isn't necessarily evil or mean. She is perhaps wandering around in a confused state, trying to figure out how she died. Wanting to catch glimpses of herself. Trying to see herself. I don't think she necessarily tried to kill Lily. She merely revealed herself, like she had revealed herself to Iris. But it's possible she knew that because of Lily's nature, it would kill her. But not necessarily.
Lily stays in the house, apparently, as a ghost, like Polly. To catch her last moments. To see herself in her human life. Not sure why. Maybe she has nowhere to go. She no longer has to stay to know how she died, because I THINK she says she knows, now. Maybe she just likes it there.
I don't know why YOUNG Iris is upstairs in her red sweater at the end of the film. Did Lily go back in time? In the beginning narration she does say that the ghost who stays goes back and forth, wandering in confusion. Or is the young Iris yet another ghost? The old Iris had died by then. I can't figure this one out.
Why does Polly stop talking to Iris? I think maybe one of two reasons: Polly wants to know how she died and wants others to know. Iris writes a book about Polly, so Polly's goal is accomplished? But the book doesn't tell how Polly died. And the movie doesn't say that Iris knows. Maybe Polly was angry that Iris had written a book about her? OR maybe Polly is angry that Iris didn't have the wall opened up or hadn't figured out where Polly's body is?
In the scene before Lily goes downstairs and dies, Polly appears to Iris and whispers in her ear. What did Polly say, and why did she appear at that time, after, according to Iris, Polly hadn't spoken to her in a long time? Well, in a scene before that, Iris is talking to Lily as if Lily is Polly, and asks Polly why she turned her back on Iris repeatedly...so much that her feet faced backward. Iris was emotional and hurt. I think that Polly appeared to Iris to speak to her one last time, knowing Iris would be dying soon. What did she tell Iris? I don't know. Maybe that if she hangs around, she too will rot, like Polly?
When Polly whispers "this is how you rot," when Lily is naming the flowers in the kitchen...is Polly telling Lily that she's going to die? Or is she warning Lily that she will rot like flowers if she stays in the place she dies?
Polly is not walking backwards near the end, any more. When she goes to whisper in Iris' ear, she approaches face and body forward. Same thing when she is following Lily as they pass by the boys' room at the end.
So are there now 3 ghosts in the house, all arranged to be there by Polly? Or just chance that three people die in the house and decide to stay to glimpse themselves in their former lives? Or were Iris' and Lily's deaths accidental? And are there only two ghosts in the house at the end (Lily & Polly)? These are things I don't know, and maybe we're not supposed to know.
Oh, and the colors that I and some others have noted: The house is painted outside & in all white (with brown wood) with some gold curtains. Lily's official outfit is all white with a gold sweater that matches the curtains (and brown hair). When she walks in, it's as if she fits in with the house. She belongs there.
Fascinating movie and one of the best ghost stories I've seen in ages. Very well done.