Doctor Who: Colony of Fear

This is the final Sixth Doctor release of Big Finish's main monthly range, before he was moved to his own series (and antepenultimate release in the series overall). As such, it's standalone, fitting early on in Constance's travels in the TARDIS, before she was joined by Flip.

As you might guess from the title, it's a base-under-siege, with the giant hornets on the cover being the creatures responsible. In this respect, it's a standard format for the series, with human colonists being menaced by an alien threat. The threat does eventually turn out to have some unusual properties, but even there, it's nothing we haven't seen before with different aliens. Aside from the fact that this is well done, however, there's an additional twist in the form of a subplot concerning a previous visit to the planet by the Doctor that he has no memory of.

This latter mystery doesn't really become important until the second half and even then, the full details of exactly what happened are left vague (although one can infer quite a lot). It makes good use of time travel, as well as highlighting some of the Doctor's flaws, and it's what lifts this story above the routine. Constance is also used well, getting plenty to do and once again making an excellent companion for this particular Doctor.