After a famous robbery, Frank and Jesse James hide in Walnut Grove while bounty hunters are in pursuit.
You can almost see Michael Landon get excited on learning that the James Brothers staged a well-known hold up in Northfield, Minnesota (not particularly close, but not that far from Walnut Grove) and deciding to incorporate a more classic "western" into his series. At the same time, this show was produced at about the same time that the country was re-evaluating history and motivations behind it - sometimes from a rather simplistic 70s perspective. The messages here aren't bad for a more modern time, even Miss Beadle's class assignment on the motivatons behind the Civil War are interesting (if hopelessly innacurate for the time period the series is set in).
Its just not seamless, and season 4 seems to show the beginnings of a corruption of the show's cohesive quaities ("My Ellen", and "The High Cost of Being Right" are not stories from the 1800s). There is no doubt that Hollywood became successful with westerns, not "midwesterns" but integrating the two doesn't quite work.
There is no gunplay here, but the idea that a gang of bounty hunters (loosely knit reward hunters not often even licensed in the 19th century) could somehow keep the town hostage in their pursuit of the James's is a little out there, and while its a nice idea to make Frank a kind and intellectual character, it just doesn't wash with history. Actually, I think the idea of outlaws on the run could have worked without the baggage of Jesse James - the sense of reality would have been better and the coincidences not so hard to swallow.