Doctor Who was now in it's third season of having the Doctor marooned on Earth and it was obvious people were getting a little bored with the format. The Timelords were now (sort of, and secretly) sending the Doctor on missions. The year before they sent him on a mission and this year they have done the same thing. The Doctor believes he has fixed the Tardis and pilots it to Peladon, only later does he admit the Timelords must have sent him.
The Tardis has landed on a rocky cliff, and once the Doctor and Jo step out, the Tardis tumbles down the mountain. The Doctor assures Jo the Tardis is indestructible (This is the first mention of that). Making their way into the Peladon council, they are taken as Earth's delegates. It seems Peladon is considering joining the Galactic Federation, along with other noble races.
Alpha Centauri (the slug-like creature) is another delegate along with the Ice Warriors, much to the Doctors surprise. When several attempts are made on the delegates lives, the Doctor assumes the Ice Warriors are once again to blame. It turns out, however, they are not and claim to have renounced their warrior ways.
Another of the delegates arriving to discuss the possibilities of Peladon joining the Galactic Federation is Arcturus. He is actually in league with Hepesh of Peladon to try and stop Peladon from joining the Galactic Federation. Hepesh believes the Federation will exploit the planet of all minerals. And that's exactly what Arturus intends to do to Peladon if they don't have the protection of the Federation.
When Arcturus attempts to kill the Doctor, he is slain by Ssorg the Ice Warrior who is returning the favour when the Doctor saved his life earlier. Hepesh then initiates a coup and uses Aggedor to do his killing for him, but the Doctor has tamed the beast and turns on Hepesh instead. Crisis averted, the Doctor and Jo discreetly leave once the real Earth ambassador has arrived.
NEXT: The Three Amigos