Greatly enjoyed THE ORIGIN OF EVIL (L'ORIGINIE DU MAL) yesterday: a little bit GONE GIRL, a little bit SALTBURN. If you intend to see it, I recommend not looking at the Wikipedia description which unfortunately reveals far too much about the film.
I'm no stickler for spoilers but I think the respectful way to summarise films is to intuit which information the filmmakers obviously do not intend the viewers to have at the start.