The operable term for this episode is, "Jumping the shark!" The term was coined after the long running series "Happy Days" literally had star character Fonzi ski jump over a shark pen. Since then, the term is applied to a series that thinks it has to explore truly bizarre themes in a desperate effort to work up something new.
Sadly, after 20 outstanding years, even Gunsmoke finally jumped the shark with this turkey!
The theme is well past implausible. In the United States, where people are free to come and go, the notion that an entire town of people wouldn't have one person in several years manage to leave town long enough to alert reputable authorities! No, that's nuts! And this foolish basis ruins the episode immediately.
Fortunately, the series did not end with this episode, as the season ran a full 24 airings in this final twentieth year. And some of those final four episodes were truly outstanding efforts.
The characters are nearly all one dimensional except for one, who is a caretaker who at first is just trying to cynically survive, but eventually comes to recognize an opportunity to escape the hell hole. In the end, his character provided the means by which the seedy enterprise was ended. Hal Williams therefore provided the only real noteworthy performance, even though the way his character spoke one could be forgiven for thinking he was played by a younger version of Scatman Crothers.
This is one of the few Gunsmoke episodes that should have been shelved and started over again.