What is the key to a horror movie? Natural or man-made disaster? Mysterious phenomena? Serial killers based on a true story? Irritating soundtrack? Super realistic CGI? Complex psychological distortion? Bascially, Asian is good at psychological, like Japanese and Thailand, while American is good at special effect, such as blood and stumps everywhere. This one is produced by America but it's not ordinary.
Not having seen lots of horror moives, I just took a quick glance at the two general genres. The blood genre shock me with the imaginative scene, some particular torture even leaves some trauma, which freezes my blood and makes me concerned about the antisocial. The other one, well, what should we say, is extremely frightened at the deep thought afterwards. Especially some details connect the real life, not that much stimulation on surface, but weird enough to make you umcomfortable. Think about it, you go to a place where everyone seems excessively to care about your healthy condition, appreciate you as a rare product. They keep observing, keep judging, keep praising. All of these words and sight softly creep into your brain.
Exactly, all the foreshadowing is a part of the hypnosis. The other black man's appearance just form the last piece of puzzle. If you want to hypnotize someone, the first step is to make him believe what you are up to. Another American horror movie named Skeleton gives a perfect sample on this rule. However, the twist in plot in the end seems like part of regulation. As a horror one, it must make some suspense. On the other hand, it may become a guideline for a sequel. I don't want to spoiler the details. Someone criticized at the beginning you might consider this a white discrimination movie but the core is still black discrimination.
The plot builds like a slow boil to a terror explosion. Both ambience and pace are great. This official post reminds me of black mirror, which is suspenseful enough yet not scary. At least not so good as the trailer post, it's more creepy. The more desperate you feel during the process, the more thrilled you get at the end of the story. Also, we can imagine how excited a group of black people watch it to the end.
In the Greek myth, Procrustean was a rouge smith and bandit from Attica who physically attacked people by stretching them or cutting off their legs, so as to force them to fit the size of an iron bed. It's even worse than racism. People always fear everything they can't understand. Then we try to make different thing the same. The truth is that we don't become completely free by just avoiding to be a slave; we also need to avoid becoming a master. There is still a long journey to go.