the story: Barclay finds unusual passengers in his transporter beam.
similar to: "Vanishing Point" (Enterprise)
my thoughts: Star Trek characters having a transporter phobia is a franchise trope all to itself (see: McCoy, Pulaski, the characters of Enterprise). The fact that Reginald Barclay is a part of that list should surprise no one. This guy was created to be the most neurotic character ever, and "Realm of Fear" is the second best episode to depict him in this mode (amazingly, he would eventually be allowed a little more nuance in Voyager).
Aside from his introduction and social anxiety in "Hollow Pursuits," Barclay actually walks away from his problems fairly well, and it's "Realm of Fear" that helps him along. The whole episode is kind of like a guilty response to "Pursuits," which presented a one-dimensional portrait, whereas "Realm" acknowledges that sometimes there really are good reasons (other than, you know, psychological ones that really aren't appropriate fodder for jokes, thank you very much Big Bang Theory, which I kid because I love) for a person's behavior, like evil monsters hiding in the transporter beam. Which in turn are revealed to be lost people trapped in the matter stream.
All of it is a much bigger thought process than mere technobabble normally allows Star Trek, giving us insight into the workings of the famous Star Trek transporter (although it's kind of frightening to think that a piece of functional technology is such a cause for concern for all these characters, like if TV shows set during our contemporary times had a lot of characters fixated on the horrors of mobile phone usage), and giving Barclay his due ("The Nth Degree" doesn't really count) in his last major appearance of the series.
Also, it kind of sets up "Relics" a few episodes later, if you think about it...
criteria analysis: franchise -
Dwight Schultz (Barclay)
Colm Meaney (O'Brien)
Patti Yasutake (Ogawa)