The Doctor and new companion Mel land aboard Hyperion III, answering a distress call, and end up having to solve a murder.
It's been a while since we've had a space whodunnit, the last probably Robots of Death. Overall I'm not a huge fan of Terror of The Vervoids, but this first episode I have always loved. It has a murder mystery feel, it's a real change in direction, it works so well early on here. Even Colin's had a slightly toned down waistcoat, all the better for it.
The Trial itself is now beginning to get serious, the tone in the courtroom is less frivolous than in the earlier ones.
Mel is great also, a terrific start for her, and I just love Honor Blackman, hard to believe she's sixty here.
Best of all, is that great big, explosive cliffhanger, the best the show had had for many years, brilliant.
I'm a little less confident with later episodes, but Part one is hard to fault. 9/10