So many clues given away...
1) Locked doors
2) Windows with bars
3) A video of a woman while she's dying
4) The uxoricide
5) Eden slapping her friend's face
6) No phone coverage
7) No wifi
8) The nympho whispering weird stuff to Will
9) Miguel's birthday celebrated a week or so in advance
10) The pills
11) Two strangers showing up at an old friends' reunion
And yet no one but Will (and Claire) suspects anything, or even feels freaked out enough to leave. How's that even possible?
And the viewer is also offered more hints that the hosts are completely nuts: lighting up the red lantern (it was soooo clearly a signal for someone else) and the video of the cult leader (and btw, you open up a laptop and there you have a video of someone saying it's doomsday, the only big flaw in an otherwise very good direction).
This movie was saved by the direction but the script is just mediocre.