Basically there's a mass shooting during a political rally. But, most of the content in general revolves around the cult members (normal people) murdering other "normal people" in pretty brutal fashion to cause panic and chaos so the leader can rise to power.
Like I said, pretty touchy stuff right now, and no real supernatural elements to speak of.
Besides that, this season might be the best one they've done. Very cohesive story line, interesting characters.