One of the interesting things about The Curse of Peladon is how they've given us a medieval-looking planet and culture, with lots of corridors moodily lit by torches and windswept mountainsides where it's always night (so less medieval and more Gothic). And then into this environment they add a bunch of different aliens, who are all delegates from the Galactic Federation, there to determine whether Peladon should be admitted as a member, and this creates a wonderful juxtaposition of the old with the futuristic. This is what Doctor Who is for.
It helps that the aliens are all sufficiently different from each other (even if, curiously, they're all shades of green), to make that juxtaposition even more striking. The first one we meet is Alpha Centauri, with six arms and a head with a single giant eyeball in the center. I have to confess: I adore Alpha Centauri. It's a really striking design (and quite mobile too), and then they've added some wonderful characterization into the mix (the quick version: Alpha Centauri is a coward first and foremost, which leads to lots of great moments as the delegates' lives are being threatened). Then we meet Arcturus, who appears to be a shrunken head in an elaborate life-support system. And finally, we encounter an Ice Warrior and an Ice Lord. Yes, the Ice Warriors are back.
And into this mix the Doctor and Jo are introduced, with both posing as representatives from Earth (the Doctor the delegate, "Princess Josephine" a royal observer), present for the same reason as the other delegates. Only it quickly transpires that someone is trying kill the delegates and anyone who's in favor of Peladon joining the Federation. High Priest Hepesh, a firm believer in the old ways, thinks it's the spirit of Aggedor, Peladon's royal beast, come to wreak a terrible vengeance. The Doctor, meanwhile, is suspicious of the Ice Warriors. So it's a mystery on our hands too. Well, except for the fact that we watch Hepesh nod subtly to Grun, the King's Champion, who then goes off and tries to push a granite statue on the delegates (giving us episode one's cliffhanger). So it's not exactly the most taxing whodunnit.
Nevertheless, episode two has a bit of fun with trying to pin the blame on the Ice Warriors. We see Ssorg skulking about in the corridors, and when Arcturus is attacked, with the "servo-junction unit of his life support system" removed, Jo finds it inside a trunk in the Ice Warriors' quarters. But when Ssorg finds Jo snooping, he claims to have no knowledge of the unit and indeed appears to tell Izlyr that Jo was attempting to plant the missing servo-junction unit inside their room. Once all the confusion dies down, Jo is properly contrite about the whole matter: "I'm sorry if I might have misjudged you, but the Doctor did say you were a race of warriors." "We were once, but now we reject violence except in self-defense," Izlyr replies. But then, if the Ice Warriors didn't attack Arcturus, who did?
And while all this is happening, the Doctor (once he's finished rescuing Arcturus -- even if it later turns out that Arcturus wasn't in any actual danger) is led by Grun into the tunnels inside the citadel, only for Grun to run off in terror when a roaring sound is heard. This leaves the Doctor to wander around the tunnels, eventually finding himself inside the inner sanctum of the holy temple of Aggedor. Unfortunately, trespassing here is punishable by death (episode two's cliffhanger). Convenient that, given that Hepesh earlier told Grun to destroy the Doctor. That same scene also makes it clear that Hepesh is pretty firmly anti-Federation and is willing to do just about anything to prevent Peladon's admission. So (red herrings about the Ice Warriors aside) it's less a whodunnit and more a "how will they overcome the villain" story. But so far this has been quite an entertaining story.