Clem Peterson (Richard Cramer) has a devious plan to steal all the land and ranches in the valley. That plan involves having one of his men called Carson (John Merton) pose as a Mexican who has a claim to the land, although a phoney one at that. When Fred and Fuzzy (Fred Scott and Al St. John) have all there cattle rustled by Peterson's men they find themselves getting involved and trying to stop the scheme.
The most interesting thing I can tell you about "Knight of the Plains" is that none other than Stan Laurel was the uncredited executive producer. Now how much Laurel actually had to do with the movie is a matter most likely long forgotten but that is about as interesting as it gets.
Beyond that tit bit of information "Knight of the Plains" is just a generic 60 minute western from 1938 which saw Fred Scott playing a singing cowboy with Al St. John playing the comedic sidekick Fuzzy once again. For those who are unaware Al St. John played the character of Fuzzy Jones in over 80 movies from 1937 to 1952. And just to add to that element of typical we have a scheming bad guy and Marion Weldon playing the obligatory pretty young woman who is a friend of our heroes.
The term generic continues with a storyline surrounding the nefarious Peterson and his skulduggerous plans to steal all the land and ranches in the valley. To say that Fred and Fuzzy end up saving the day is technically a spoiler but not much of one as you expect nothing else from one of these quickly made westerns from a bygone age.
What this all boils down to is that "Knight of the Plains" is just a generic western from 1938 with some familiar faces working a familiar story. So again this is another movie whose only appeal is to those western fans who said "challenge accepted" to watching every western ever made.