Festival of Death

At its heart, a straightforward zombie apocalypse story set on a space station. But what lifts it above that, aside from some good characterisation of the leads, is the complex weaving of time travel through the story, with the Doctor and Romana travelling to various different points within the story out of sequence. The story is told in a linear fashion from their perspective, but that's certainly not the way things are unfolding for anyone else.

More the sort of thing you'd expect from Steven Moffat than from Graham Williams (the producer during the era of the show within which this fits), but none the worse for that. Quite a fun read.