Took me a while to get round to this purely because some of the reviews were very negative.
When I did eventually watch it, I was so glad I did.
It's a great little mystery horror. Despite a low budget, the cinematography is great, the acting is on-point (with a few forgivable exceptions) and the script is clever. Theres' a twist that is sign-posted throughout but never obviously enough that it ruins the ending. I had suspicions of what was going to happen but still found the final reveal rewarding.
There are several negative reviews on IMDB but, for the most part, these seem to miss the point. In particilar, a review titled "Doesn't make any sense" misses the point entirely. There's more than one way to interpret this film and there is a lot of scope to unpick the symbolism; that reviewer clearly just took the whole thing literally.
As I said in the title, if slowburn horror appeals to you, and you don't mind lower-budgey (but still very well made!) indie films, you could do a lot worse than this!