It seems like it's been a long time since we had a 'base under siege' episode, which is a shame - as far as Doctor Who episodes go they are often amongst the best (such as The Waters of Mars or Midnight) thanks to the way they confine The Doctor to one space and make him use his own intellect in order to solve the problem at hand. Not only that, but the focus on the monster of the episode often makes them more... well, not scary exactly, but at least more tense that the average episode of Doctor Who.
"Under the Lake" sees The Doctor and Clara stumble upon an underwater mining station that, as we learn from the episodes pre-opening credits scene, is apparently being haunted by what appear to be ghosts after the crew of the mining station found a spaceship. After accidentally making the ghosts target them, The Doctor and Clara join up with the remaining crew members in order to try and figure out what is going on.
"Under the Lake" uses the confined and claustrophobic space that the episode is set in to provide a thoroughly entertaining adventure - albeit one without a resolution thanks to the episodes status as the first half of a two-parter, something that I'm hoping the rest of the season avoids for at least a while. There is nothing wrong with a two-parter episode of course, but I feel that opening the season with one was a bad idea, and following that up with another two-parter seems as if season nine may be cashing in it's long-form stories a little too early.
Regardless, that doesn't change the fact that "Under the Lake" was a damn fine episode. I'm usually pretty frustrated in those instances where Doctor Who attempts to tackle the supernatural by providing a half-baked science fiction explanation, but "Under the Lake" doesn't try to do that - The Doctor soon admits that he has no idea what is going on, which draws his (and our) interest far more effectively than the usual Doctor Who story can. Also helping draw the audiences interest is that thanks to the fact that we see the initial attack whereas Clara and The Doctor did not, we actually have more knowledge about the situation than any character in the episode - which means that we can start to piece together what is happening before The Doctor can, which is always satisfying.
But for me the most important thing about the 'base under siege' episode is always the strength of the supporting characters, and "Under the Lake" has it where it counts. Sure, at least one of the characters in the episode is a walking archetype (bringing to mind the sleazy Weyland Corporation representative from Aliens now that I think about it), but even then his character seems more naive than malicious, and the rest of the supporting characters are a diverse bunch with distinct personalities. My favourite of the crew is Cass, a deaf woman - not only is it quite cool (and all too rare) to see someone with a disability represented on TV, but the fact that "Under the Lake" doesn't treat her as anything less then intelligent and capable is fantastic, as is the way that "Under the Lake" makes her a very important part of the story.
Add in some interesting special effects, some genuinely funny moments (The Doctor having to read off cards in order to empathise with people is near genius) and one hell of a last minute cliff-hanger, and "Under the Lake" is one of the better episodes Doctor Who has produced not just since Peter Capaldi became the Doctor, but since Steven Moffat took over as show runner. Writer Toby Whitehouse deserves and awful lot of credit for what he has managed to achieve with "Under the Lake", and I can't wait to see how the story is resolved - for the first time in a very long time, I'm actually looking forward to seeing the next episode of Doctor Who.
I still think the Sonic Sunglasses are stupid as hell though.