Sarah and I weren't very compelled by the Guillermo del Toro-produced Don't Be Afraid of the Dark, but we loved the Guillermo del Toro-presented The Orphanage. So I was prepared to go either way with this movie, also produced by GdT (not spelling that out again). And I mostly liked it.
The core story is two little feral girls get taken in by family, but bring supernatural protector with them. So it's got that "haunted person rather than haunted house" vibe. Except the protector/ghost is also tied to the location out in the woods where the horror happened, which felt a little bit like they were trying to split the difference: a scary haunted house plus the scary "your home is being invaded" trope.
The movie also leans hard into certain tropes and structures: the unethical third person (a psychologist) who does all this research; the slowly pieced together story, involving boxes that characters look into but the camera doesn't; the aloof mother-figure who fights the ghost for the children at the end.
Which leads us to some problems of structure. Jessica Chastain's punk-rock "don't call me mama" girlfriend turns out to be the protagonist, not the boyfriend who is the blood relative of the feral girls. Considering that the movie already starts with a prologue setting up the horror, this switch made me feel like I wasn't sure what to look at.
Similarly, as some reviewers note, the eventual story turns toward the routine: a crazy woman escaped from an asylum, killed herself and her kid, now wanders around looking for that kid. (La llorona?) It's never addressed, but how did she get pregnant in the asylum? Or even before--the potential story of rape might be worth thinking about.
There is one interesting issue about the ending, when ghost and adoptive mom fight over the kids, which is that each kid chooses a different mama. Unlike the ghost's original kid (who dies), the little girl here turns into moths, which makes the ending stranger and more uncertain.