There's some fantastic use of POV shots of the wounded monster in this episode as director Timothy Combe does his best to taunt and tease the viewer about what it looks like. We only have the reactions of others who are encountering the monster to go on, and, if these encounters are anything like Squire, the farmer, experienced, then this monster is very strange and dangerous indeed.
Given that Fulton Mackay was offered, but turned down, the role of the Fourth Doctor in 1974, I'm always intrigued to watch this story to try and get some hint of how he might have portrayed the character. To be honest, I'm not sure what producer Barry Letts saw in him for the role, but he's terrific in this story, and we find out that Mackay's Dr. Quinn has struck a bargain with the strange race of monsters who are behind the power failures at Wenley Moor. Quinn's boss is Dr. Lawrence, who is played by Peter Miles, who is always so good in anything he appears in that he'll deserve another entry later.
Speaking of Barry Letts, this story marks his debut as producer. While one can't credit him with commissioning the story from writer Malcolm Hulke (Letts only joined the production after the location footage had been shot), he can be credited, at least, with one thing that has always tickled me in just the right way. Have a look at the end credits and how each credit screen changes on the beat of the theme music. That was completely intentional and all because of Letts, and it the credits would be done this way for the rest of the classic series's run. Letts would be responsible for a great deal over the course of his time on Doctor Who, but this little touch has always been one of my favourites.