Episode two, 16 May 1970
Episode three, 23 May 1970
Episode four, 30 May 1970
Episode five, 6 June 1970
Episode six, 13 June 1970
Episode seven, 20 June 1970
Written by Don Houghton
Directed by Douglas Camfield
Script editor: Terrance Dicks
Produced by Barry Letts
Jon Pertwee as the Doctor
Nicholas Courtney as Brigadier Lethbridge-Stewart
Caroline John as Liz Shaw (last regular appearance)
John Levene as Sergeant Benton
Stahlman's not evil; he doesn't want to take over the world, or destroy it. He's just arrogant: he's convinced of the rightness of his theory regarding the existence of Stahlman's gas, and he's so eager to get to it that he keeps speeding up the rate of drilling, regardless of any concerns for safety. He refuses to listen to any warnings--from his assistant, Petra Williams (played by Sheila Dunn, wife of the story's director, Douglas Camfield); from the project's administrator, the civil servant Sir Keith Gold; from Greg Sutton, an oil-drilling expert the government has brought in from a drillsite in Kuwait; or from the Doctor, who's hanging around the project because he's hooked up the TARDIS to its nuclear reactor for some experiments he's running in his continuing quest to overcome the exile imposed upon him by the Time Lords. UNIT are also hanging around, in order to ... well, actually, I'm not sure why UNIT are there, but they're there.
(A casting note: Derek Newark, who plays Greg Sutton, played Za in the Doctor's very first adventure in 1963, while Christopher Benjamin, here making his first entry into the programme, as Sir Keith, most recently appeared in Doctor Who in 2009, opposite David Tennant and Catherine Tate. So in "Inferno", we've got 46 years of Who history playing opposite each other.)
But there are problems besetting the project. Something is happening to a few of its technicians, and to a few of the UNIT soldiers: they're turning into hairy green monsters who are burning hot to the touch, and who are horribly strong and manically homicidal. Unbeknownst to the main characters, this metamorphosis is caused because the unfortunate individuals are coming into contact with a strange green slime that's been oozing up from the drill head deep beneath the Earth's surface--the drilling is unleashing dark forces from the Earth's core.
The story takes a sudden, unexpected swerve when one of the Doctor's experiments with the TARDIS goes awry. The TARDIS dematerialises, but it takes the Doctor neither forward nor backward in time. Instead, he rematerialises in the same place and time, but in a parallel reality--an alternate history. He soon discovers that he's somehow transported himself to a world where Britain abolished the monarchy in 1943 and turned into a brutal, right-wing fascist dictatorship.
Everything is present in the alternate world that was present in the real world, but it's been twisted. The Stahlman's gas drilling project is still going on, headed by Professor Stahlman, but now the project is at a "scientific labour camp"--meaning slave labour. The UNIT team are still providing security, but not as UNIT--they're now members of the Republic Security Forces. They're led by the Brigadier, who has lost his moustache and gained an eyepatch and now goes by the rank of Brigade Leader. His second in command is the stern, no-nonsense Section Leader Elizabeth Shaw, who's a far cry from being any sort of scientist.
(The "leader" ranks are a nice touch--even Benton is ranked "Platoon Under Leader". It's an echo of Gestapo ranks, which all ended with -führer, from Reichsführer, the unique rank held by Heinrich Himmler, all the way down to Unterscharführer, or Squad Under Leader, the equivalent to lance-corporal or PFC.)
Of course, the Doctor is quickly apprehended by the dark, brutal counterparts to his friends from UNIT, who conclude that he's a spy for a foreign power. So he has to avoid getting put in front of a firing squad, but he's also got another concern--figuring out what's going on with the drilling.
The alternate-world drilling project is further along than its real-world counterpart, and the Doctor is present when it penetrates to the Earth's core. And it might surprise you to learn, but the result isn't the discovery of a new, inexhaustible energy source--it's the end of the world. Tremors begin all across the country, and spontaneous volcanoes form. The Doctor realises it's only a matter of a short time until the Earth's entire crust breaks up.
As the situation deteriorates, people's true characters come out. The Brigade Leader becomes even more militant, more shrill, more megalomaniacal, convinced his vaunted Republic will save everyone. (Nicholas Courtney is clearly relishing playing a shrill, paranoid villain.) But Section Leader Shaw is gradually coming around to the Doctor's story of where he comes from, and she's showing a willingness to help the Doctor get back to the real world so he can save our own reality from suffering the same fate as hers.
Which is, of course, what happens. The Brigade Leader hatches a plan to force the Doctor to take him back with him to our reality at gunpoint, but of course it doesn't work. The Doctor makes it back alone, and he's able to stop the drill just before it penetrates the Earth's mantle. One world has died, but the other has survived.
What Lisa thought
She really didn't like it. She found it slow and turgid, and she's finding the UNIT format really repetitive. When I told her "Inferno" is one of the most highly regarded Whos of all time, she asked, "... But why?"
She did like Evil Liz's look--she thinks Carolina John looks good as a brunette.
It's a shame, because I, like most of Who fandom, is really neat--the opportunity to see Britain as a fascist state, the opportunity to see UNIT turned to evil, and the opportunity to see Benton metamorphose into a green, hairy monster.
The next story is "Terror of the Autons".