The planet Peladon, under the rule of its young King Peladon (David Troughton), is petitioning to join the Galactic Federation. Its delegates are just about to cast the final vote. The High Priest Hepesh (Geoffrey Toone) is opposed, warning of the Curse of Aggredor, the Royal Beast of Peladon. It means doom. The TARDIS materializes on the edge of a cliff below the castle. The Doctor and Jo have no sooner left the ship than it tumbles over the edge, and they are forced to climb to the castle for help.
King Peladon wants Hepesh’s support, but the old priest doesn’t trust the Federation—they’re all a bunch of aliens. The Doctor and Jo are found by the Palace Guard, who take them to the Throne Room, where the delegates are gathered. There is Alpha Centauri (voice of Ysanne Churchman and body of Stuart Fell), who is a bulbous alien with six arms and a spherical head with one large eye. There is Arcturus (Murphy Grumbar puppeteer and voice of Terry Bale), who is a green head in a glass bowl on a little cart like a robot waiter. And there are two Ice Warriors—Lord Izlyr (Alan Bennion) and Ssorg (Sonny Caldinez). The Doctor is thought to be the representative of Earth, but who is the young lady with him? As a person of rank, he may enter the Throne Room, but unless she is of royal blood, she must be killed. Jo immediately begins putting on airs and talking with a haughty, high-class accent, so the Doctor introduces her as Princess Josephine of TARDIS. The young king is instantly smitten. The Doctor requests that his shuttle be hauled up from the bottom of the cliff.
Accidents begin to happen and delegates die or are attacked—the statue of Aggredor topples and nearly kills someone and Jo finds clues--and the show becomes something of an Old Dark House Story. Exploring the subterranean tunnels, the Doctor is pursued by the Monster Aggredor (Nick Hobbs) a roaring furry creature with horns and tusks, who unfortunately looks a little like ALF. Fleeing, the Doctor ends up in the Shrine Room, before an ancient statue of the same creature, where Hepesh discovers him and accuses him of sacrilege. He must endure trial by combat with the Royal Champion, but Hepesh offers to let him to escape if he will leave immediately. They encounter Aggredor again, and Hepesh calms it by singing.
The Doctor tries to tell King Peledon what he knows of the beast, but Hepesh again orders that he be taken away to battle the Royal Champion, a very tall deaf-mute Grun (Gordon St. Clair). He is powerful, but the Doctor defeats him and spares his life. Arcturus tries to kill the Doctor but is shot by Ssorg. Arcturus and Hepesh, it is revealed, are behind a conspiracy to frame the Ice Warriors. Hepesh found the Aggredor creature, thought to be mythical, in the mountains and trained it to keep the myth alive, all in the interest of an agreement with Arcturus concerning Peladon’s valuable mineral deposits.
The vote for membership carries, but the delegates cannot communicate with their ships. Hepesh and his secret army attack the Throne Room and hold Peladon hostage. He must return to the old ways or die. The Doctor arrives with Aggredor, whom he has hypnotized into obedience. The creature immediately attacks and kills Hepesh, and his army swears loyalty to Peladon. On their way to the King’s Coronation, the Doctor and Jo see the real delegation from Earth arriving and beat a hasty retreat in the TARDIS. They realize that this was exactly the sort of task the Time Lords would like the Doctor to do, and the TARDIS is still not free.
Alpha Centauri had a rather phallic shape and was given a cloak to cover up. The Venusian Lullaby the Doctor sang to Aggredor to calm him was to the tune of “God Rest Ye Merry, Gentlemen”. David Troughton is indeed the son of Patrick Troughton. Someone suggested that the whole story is about Britain joining the European Union, which pretty much takes all the fun out of it. I don’t believe Doctor Who is going to do a Brexit story soon.