Jack Herbert’s review published on Letterboxd:
What's he building in there?
I'll tell you this,
It's not a playhouse for the children.
A smashingly good, intuitive, complex and astonishingly felt Rebecca Hall performance in service of a film that, for the first two thirds, takes seriously grief and pouring over and simply reckoning with who one's significant other was (or is dun dun dun), and is more engrossing as a marriage drama and peculiar and even surrealist mystery than a horror movie. I like the concept of a wife discovering her dead husband who she (thought) had a solid marriage discovering a lot more than she could have expected to be unsettling in a satisfying sense.
But the drama being more coherent or less self serious than the horror is far more amplified by the final third where it reveals its cards and it starts to make the movie make much less sense than at least where I thought it was going (and it raises more questions than it can hope to answer, not least of which because we don't get any sense earlier what their marriage was like - that it's told and not shown, not even a little montage like in Annihilation or something). It's a letdown, in the sense that you want it to go into an area that if it can't be dramatically intriguing anymore than is successfully terrifying past the surrealism, and it isnt.
I'm still glad a screenplay that was just written and got lit and produced and released by a studio on many screens is happening. Maybe next time though I shouldn't take for granted when one of those producers is David S Goyer (latter day Goyer I mean, I know he has some excellent work). I'll pay it one more compliment: this admirably aspires to a certain sort of psychosomatic emotional terror that Ingmar Bergman was after in his late 1960s films (ie Shame, Hour of the Wolf, Persona of course with its emphasis on Doubles), it just couldn't quite work out the logistics of the script it makes for itself.