The plot twist comes directly fromSPOILER

Rating: Null/10 (23 June 2017)

I'll leave the spoiler to the very end. The start of this movie, where a white girl Rose brings her black boyfriend Chris to see her unknowing parents, looks very much like "Guess who is coming to dinner" (1967, fetching Katharine Hepburn one of her 4 Oscars) . But here it is more than just dinner, but a weekend at their suburban home in an upper middle class white neighborhood. The parents Dean, a neurosurgeon and Missy, a psychiatrist welcome Chris warmly, maybe a little too warmly. The only fault they find with their daughter's new boyfriend is that he is a smoker, but he assures them he is quitting. Missy offer one session of hypnotism which she gaurantees will cure him once and for all. He politely declines.
A not-unexpected slight discomfort for Chris is encountering the two black servants Georgina and Walter. Dean explains that they were actually hired to take care of his aged parents. When the parents pass away, he kept them around for their loyalty. Note this bit of detail.
Nothing seems really abnormal as Chris gets to meet Rose's younger brother Jeremy (just a tad eccentric), and later a big assortment of the family's neighbors and friends, in a big party. There is nothing you can categories as abnormal and yet there are lots of encounters and exchanges that goes from subtly irritating to outright creepy. In particular, the only black guy the meets, Logan, is the husband of a wife twice his age. Note this bit of detail.
I'll get to my summary line and the spoiler now. The movie I am referring to is "The skeleton key". If you remember that one and note the two bits of details I pointed out above, the plot twist becomes painfully obvious. The difference is in that movie, the host "soul" is switched to the ageing while here it plunges into a sunken place still inside the host's body with just a flicker of consciousness (even more horrible).
Casting is good. The two protagonists Daniel Kaluuya and Allison Williams contribute to the movie's success. The only one in the cast I know, however, is Catherine Keener, arguably the best character actor around, playing Missy. One character I have not mentioned, who appears briefly together with Chris at the beginning before the latter leaves town, is buddy Rod. Throughout the movie, he is virtually and literally Chris's life-line, at the phone (maybe not too literally because we use cell phones these days). He appears in the very end, carrying through this role, to rescue Chris. LilRel Howery is excellent, providing the only comic relief quite essential to bring some balance to this movie.