Wikipedia lists this as "science fiction horror." I wonder about that: "unexplained events" can just as easily fall under fantasy, and is it "horror" when a lot of creepy (but mostly not horrible) things happen?
Two brothers (the directors, Justin Benson and Aaron Moorhead playing "Justin" and "Aaron") who were raised by a commune in the hills, have different memories of the place: the older claims it was a UFO death cult, the younger remembers a friendly commune. The life they've had since departing the commune has been poor both financially and emotionally, and they eventually go back to say goodbye and wrap things up. Initially it seems Aaron was right: they're welcomed back, people are friendly, they're served a good meal. But while the people remain friendly, strange things happen around them.
The story is mostly about the two brothers working out their problems, something that's re-enforced by a quote at the beginning of the movie: "Friends tell each other how they feel with relative frequency. Siblings wait for a more convenient time, like their deathbeds." The movie attributes the quote to "Unknown," but I suspect it can be attributed to Benson and Moorhead (all Google references to that quote point back to the movie). But it's an interesting observation, and does clearly outline one of the themes of the movie.
It's low budget: unknown actors and simple special effects with some (well done) CGI. But it's well written and consistently interesting: I really enjoyed it.