I'm not even sure what the mystery is in this season. I found season One to be an interesting and well written show, mostly based on the writings of C. J. Box, even if it detoured off into it's own thing. And even if it did, the first season and parts of the second season were a good representation of the "World" that Box has created in his novels.
There was always a strong story thread through the first season and a half that was fun and interesting to follow. Even toward the end of Season Two, most of that thread remained, despite the wacky new thread that was introduced. This season? The thread that is there is uninteresting and we've seen it all before. The characters somewhat resemble characters that you might find in a C. J Box novel, but not in the subtle way that they appear on the printed page. And the format has gone from epic story lines to a more episodic one, meaning the characters are resolving plot lines within each episode, rather that over the course of half a season. That just makes it another cop show. We've seen all of those already.
The new sheriff is dumb, dull, and not a good representation of what C. J. Box is known for. Why is his ex wife's boyfriend camping with his daughter? And why did it take so long for her to show up? What's the deal with the airplane tech whistleblower story? So, those are the big threads for this season? Sure, Walter is creepy, but not Ronald Pergman creepy. He's just a run of the mill psycho living out in the woods. We've seen that before as well.