Upon seeing the old bearded man running towards the screen through the mist and bushes at the onset of the story, no, it isn't the "It's..." man from Monty Python's first season. Rather, it's a mutant native of Solos, derogatorily called "Mutts" by the Marshal of Solos.
The appearance of a small sphere resembling a cross between a basketball and a coconut is a three-line whip from the Time Lords to the Doctor, a task that's an emergency. The TARDIS takes the Doctor and Jo to a Skybase hovering over Solos in the 30th century Earth Empire. "Once [Earth] sacked the solar system, they moved on to pastures new. Solos is one of them, one of the last [to gain independence]. Did you ever read Gibbons' Decline and Fall?... Empires rise and empires fall."
They instantly fall in trouble. The Marshal, the blustering, stout colonial ruler of Solos with piggish eyes and expression, is stunned to hear that Earth is finally giving Solos its independence. "We can't afford an empire anymore. Earth is exhausted, finished, politically, economically, and biologically," says the Administrator (Geoffrey Palmer). In a panic, the Marshal has the Administrator murdered, then imposes martial law to continue his reign over Solos, which has been exploited for its thaesium. Ky, leader of the more radical natives, is not only framed for the murder, but the sphere is intended for him.
The Doctor, Jo, and Ky are befriended by two of the Marshal's guards, Stubbs and Cotton, who learn of the Marshal's plot and see Solos as a "stinking rotting hole" that should've been given independence years ago. The planet is grey, but that's nothing compared to the Doctor's description of 30th century Earth, "land and sea alike, all grey. Grey cities linked by grey highways across grey deserts. Slag, ash, and clinker. The fruits of technology." Hmm, sounds like 20th century Earth to me.
But the Marshal also has a dream to turn Solos's atmosphere into one breathable for humans and to heck with the Solonians. Experiments by his scientist Jaeger has caused pollutions that have caused the mutations among Solonians. At least, that's the ostensible explanation. "Genocide as a side effect? You ought to write a paper on that, professor," the Doctor angrily tells Jaeger. As for the mutants, they resemble giant, grey, large-eyed armoured insectoids.
Paul Whitsun-Jones pulls in a strong performance as the sadistic Marshal, accused by the Doctor as being responsible for "one of the most brutal and callous series of crimes against a defenseless people it's been my misfortune to encounter." Indeed, the Marshal ranks as one of the most heinous villains in Doctor Who's history. When told he is quite mad by the Doctor, he replies calmly, "Only if I lose." And George Pravda (Jaeger) would later play Castellan Spandrell in The Who story The Deadly Assassin.
There are three elements in this story comparable to The Empire Strikes Back. One, the navy blue uniforms and helmets of the guards are similar to that of the Bespin Guards. Two, the Skybase and Cloud City float above their respective planets. Three, John Hollis, who plays Dr. Sondegaard here, also played Lando Calrissian's bald android assistant, Lobot. And speaking of Star Wars, Garrick Hagon (Ky) played Biggs Darklighter, Luke's best friend from Tatooine who ends up being toast in the Death Star battle.
Also, this was the story Saladin Chamcha watches in Salman Rushdie's The Satanic Verses, only it was mistakenly called The Mutilasians.
Despite being criticized for its overlength and bad performances, this allegory on the fall of the British Empire and apartheid is thematic of British guilt in the 70's for exploiting native peoples, and a striking Pertwee story, well worth its six episodes. John Hollis, Rick James-no, not the Superfreak, (Cotton), and Christopher Coll (Stubbs) lend credible support. The mutants are effectively realized, with the Doctor and the lovable Jo still a great team.