Short: Don't read the synopsis and watch it, you'll figure it out when it ends, hopefully.
Long: To be honest, the synopsis and any other spoilers about the film kind of ruin the revelation of the ending of the movie, and if you want a good experience of a movie that's very unique and creative, yet also very dark and chilling, don't listen to anyone talk about if until after you've watched it, and I also don't recommend reading too much of the synopsis, since it kind of spoils the 2nd half of the movie. I think it would be much better to watch it without knowing what's happening and then have the slow realization of what's truly going on, but perhaps the reason what happens is supposed to be obvious in order to push it's main message, but I just think it would've been better as a surprise what happens.Overall a good movie, just wish I hadn't been spoiled about it, might've made the experience more impactful.