At some date in the far future, the planet Pluto is habitable by humans, being warmed by six artificial suns. The planet's political and economic structure, however, do not make it a very desirable place to live. The inhabitants live under the rule of an all-powerful, oppressive Company which has created a police state and extorts money from the citizens through excessive taxes. When the Doctor and Leela arrive on Pluto they join forces with a group of discontented citizens to spearhead rebellion against the power of the Company.
On the face of it, therefore, "The Sun Makers" seems to be preaching a straightforward left-wing message. All capitalists are bloodsucking parasites! All hail the Revolution, comrades! (Tom Baker's Fourth Doctor always struck me as one of nature's radicals, just as Jon Pertwee's Third always seemed a natural-born conservative, and the bolshie Leela was said to have been based in part upon, and named after, the Palestinian terrorist Leila Khaled, even though Khaled's first name was actually pronounced "Lyla").
Beneath the surface, however, things are not so simple. The ostensible left-wing agenda might hide some more right-wing satire. The serial was first broadcast in 1977, a time when Britain had a left-wing Labour government which seemed to regard high taxation as a matter of principle and a Conservative opposition which promised to cut taxes. (The writer Robert Holmes claimed it was a satire on his own experiences with the Inland Revenue). The Company is headed by a corrupt and malevolent official known as "The Collector", whose bushy eyebrows are similar to those worn by the then Chancellor of the Exchequer, Denis Healey. The Collector's bodyguard, who double up as the Company's secret police, are known as the "Inner Retinue", a pun on "Inland Revenue". (To be fair to Healey, I should perhaps point out that the Collector's other main distinguishing features are a bald head and a high-pitched voice; Healey had a full head of hair and a deep, sonorous voice which made him a natural target for impressionists).
As one might imagine, "The Sun Makers" is more concerned with political satire than with hard sci-fi, and is light-hearted rather than serious in tone. I doubt if many children took refuge behind the sofa while this one came on the telly. Even the Collector is more ridiculous than frightening. Baker, however, is on good form and he receives excellent support not only from the lovely Louise Jameson as Leela but also from his most curiously endearing companion, the robot dog K-9. There is another good performance from Richard Leech as the Collector's blustering, obsequious underling Gatherer Hade. This is one of the most amusing of the Fourth Doctor's adventures.