I didn't know much about this movie going in; it was one of Mrs. Salad's picks. Just the Netflix description:
Confronted with the potential end of their marriage, Ethan and Sophie take off for a weekend together, hoping to negotiate their future. When they reach their idyllic destination, however, the couple strolls into a bizarre new brand of trouble.
Ethan is played by Mark Duplass and Sophie by Elizabeth Moss. Their whiny mutual insecurity is played for some very subtle humor at the start. They go to a marriage counselor, and before you can say "Hey, that's Ted Danson", they are off to a very nice estate where they are to spend some time alone together.
Except: are they really alone? Pretty soon the movie takes an unexpected turn into what Sophie calls "Twilight Zone" territory. I can't really say any more here without spoilers, but it's a very clever script that sneaks up on the viewer.
I was impressed by the acting talent of both Mr. Duplass and Ms. Moss. But (again) I can't go into much detail about that without spoilers.