Clark Kent and Lois Lane travel to Silsby, Texas, site of the deepest well ever drilled. But when they arrive, the well is being shut down and the oil company manager present isn't saying why. Meanwhile, two short beings with large heads and furry hands come up from the well to explore. Luke Benson leads a mob of townspeople wanting to kill the "unknown people." Despite Superman's efforts to calm things down, the mob has tracked the two creatures to the top of a dam, trying to kill them. What the mob doesn't know is the creatures cause things they touch to glow in the dark -- and may be radioactive.

[Episode 25 and 26 together were originally the movie "Superman and the Mole-Men" (1951). Information from http://fandom.wikia.com/:

"Superman and the Mole Men is a 1951 black and white film which later aired as two episodes of the Adventures of Superman TV series called "The Unknown People."

It was the first theatrical feature film based on the Superman characters (although two live action Superman films had already been shown in cinemas, they appeared in a serial format). With an original screenplay by "Richard Fielding" (a pseudonym for Robert Maxwell & Whitney Ellsworth), it was shot in 12 days on a studio back lot. It served as a trial run for the syndicated TV series Adventures of Superman, with George Reeves and Phyllis Coates reprising their film roles as Superman and Lois Lane, respectively."]