Doctor Who: Prisoner of the Sun

This is, in many respects, quite a high-concept story, in that some of the basic ideas behind the setting are very impressive, and the sort of thing that might work well in, say, a novel that could really explore their implications. Unfortunately, here, they're just a rather cool backdrop to a merely average story.

But the background does, indeed, have some brilliant ideas, with the entire tale set on a space station built within the blazing interior of a star, and operated by beings of liquid mercury. Furthermore, there's the Doctor's robotic companion, designed to replace Lucie (and voiced by the same actress). This makes for an interesting dynamic, but all we really get is some running around on the space station as unexpected visitors turn up, and then just about everyone lies to everyone else about what's really going on.

With no particular connection to the season's arc (apart from the cliffhanger at the end), this feels like treading water, rather than being a particularly effective episode in its own right. It's not a bad story, by any means, but nothing makes it stand out, either - it just fills what would otherwise be an odd-feeling gap between Relative Dimensions and the 2-part season finale.