The self-contained story is fairly formulaic as both a Doctor Who adventure and a murder mystery, with a sinister opening carried solely by the impressive guest cast as weird and inexplicable things start to happen on Fang Rock, before the Doctor comes onto the scene by random chance and sets himself up as chief investigator (claiming that although he isn't in charge, he is 'full of ideas'). The reliance on cliff-hanger endings for the first three parts could be seen as a rather desperate shock tactic to maintain interest, particularly as the crashing yacht in the first comes out of nowhere, and even more so the deaths of characters one-by-one, but the majority of the supporting characters are so well developed that their deaths (that may or may not occur, I wouldn't want to spoil things) are far more genuinely shocking than those of stuntmen or background characters in more wide-reaching episodes. The exception has to be the shrieking secretary Adelaide Lessage, whose well-spoken lady-in-distress feels fully deserving of her ultimate fate, especially when compared to the lovable, hard-working Yorkshiremen who tend to the lighthouse every day and night without being permitted a single drop of alcohol.

Like Leela, whose warrior background, it is explained, has given her a relaxed attitude towards death, it's a little disturbing to see them both sharing jokes and laughing almost immediately after an innocent person has lost their life. It's much like the closing scenes of many old Star Trek episodes, where Kirk and McCoy would make a racist joke against Spock and the three of them would smile as their starship left orbit of the planet whose society and belief system they had decimated. Leela herself stands out well despite the Doctor's prominence, her savage background being mentioned several times but absent from the opening part where she seems merely to be the Doctor's latest brunette in a loose fitting jumper. She easily has the most amusing lines, instructing the squabbling survivors that they will listen to the Doctor's instructions or else she shall rip out their hearts, and administering some satisfying face slaps to the bawling secretary. Louise Jameson carries out the whole performance in an irritated dead-pan manner that works excellently in marking her out as separate from the human characters and closer to the Doctor's spectral level, and seems only to benefit from the allegedly aloof and intimidating behaviour of Tom Baker on set, particularly in this story. Although the character isn't at her most impressive here, the scenes she shares with the Doctor make it clear that alien companions had a lot more to offer than humdrum humans, and her clear independence, despite a strong belief in all of the Doctor's actions, leads to a very nice final scene.

'Horror of Fang Rock' is a relatively slow and confined Doctor Who story and is far from unique in its survival and mystery elements, but what matters is its success as a science fiction horror story. Although the Rutan is exposed far too early in the plot, the initial evidence of electrocution and missing bodies is an exciting set-up, and this focus on electricity itself fits perfectly into the historical period of the piece, following an earlier discussion between the young apprentice and the mouldier, older lighthouse keeper on the merits or drawbacks of this new power source over traditional oil lamps. It's nice to have the human element to balance out the non-human regulars (or at least, not in the traditional sense), even if this leads to repetitive criticism of humanity's narrow-mindedness, but most of all it's great to see the Doctor's skill as a technician (pronounced 'tesh-nician' by Leela, a quick but fallible learner) figuring largely in the plot. Tom Baker effectively conveys the Doctor's sense of nostalgic wonder at these early days of electricity, and it's moments like these that make his penchant for endless time travels in an unreliable craft easier to understand.