Production Code: DDD
1 - 09/05/1970 17:15
2 - 16/05/1970 17:15
3 - 23/05/1970 17:15
4 - 30/05/1970 17:15
5 - 06/06/1970 17:15
6 - 13/06/1970 17:25
7 - 20/06/1970 17:15
The Doctor is an observer and UNIT are providing security cover at an experimental drilling project designed to penetrate the Earth's crust and release a previously-untapped source of energy, named Stahlman's Gas after its discoverer. Professor Stahlman dismisses the concerns of the project's Executive Director Sir Keith Gold and exceeds all safety margins in order to expedite the work.
Soon however the drill head starts to leak an oily green liquid that transforms those who touch it into vicious primeval creatures with a craving for heat. The Doctor is accidentally transported by the partially-repaired TARDIS control console into a parallel universe where England is ruled by a military dictatorship.
The drilling project is at a more advanced stage here and, thwarted by his friends' ruthless alter egos, he is unable to prevent the penetration of the Earth's crust, which ultimately causes the planet's destruction. Escaping back to his own universe, where the drilling is still in progress, the Doctor tries to warn of impending disaster. At first he is disbelieved, but his words are borne out when the power-crazed Stahlman is himself transformed into one of the hideous primordial creatures.
The Doctor, aided by consultant Greg Sutton, kills Stahlman with ice-cold blasts from fire extinguishers. He is finally able to shut down the drilling with only moments to spare.
The Doctor and the Brigadier discover missing maintenance worker Harry Slocum in the switch room of the project's nuclear reactor. He has mutated into a vicious sub-human creature.
The Brigadier and Liz rush into the hut in which the Doctor has been attempting to repair the TARDIS control console. They are just in time to see the Doctor, the console and Bessie all vanish.
In the parallel universe, the project workers are trying to cope with an emergency caused by a leak in one of the drill head output pipes. The Doctor tries surreptitiously to repair their broken-down computer but is confronted by Platoon Under Leader Benton, who tells him that he can either go with him to face a firing squad or be shot where he stands.
The Doctor tries desperately to persuade the project workers in the parallel universe to stop the drilling, warning that if they penetrate the Earth's crust they will release forces that they never dreamed existed. Stahlman tells Brigade Leader Lethbridge-Stewart to shoot the Doctor and then, as a distant rumbling and screeching noise is heard, he raises a gun to do so himself. The countdown to penetration reaches zero...
The Doctor, sheltering in an office with the Brigade Leader, Section Leader Elizabeth Shaw, Greg Sutton and the project's Assistant Director Dr. Petra Williams, tries to persuade them to help him to return to his own universe. He tells them that he has a plan. Suddenly the arm of one of the primordial creatures smashes through the window in the office door.
The Section Leader shoots the Brigade Leader in order to give the Doctor a chance of escaping. The Doctor tries desperately to activate the TARDIS console as a wall of lava rolls toward the hut...
The Doctor bids farewell to Liz and the Brigadier, telling the latter that he is a 'pompous, self-opinionated idiot,' and then dematerialises with the TARDIS console. He walks back into the hut moments later, sheepishly admitting that he got no further than the nearby rubbish tip. Making light of his earlier remarks, he tries to persuade the Brigadier to have his troops help in retrieving the console. Liz laughs as the two men leave the hut together.
The Quatermass serials (the installation setting, men turning into monsters, race memory).
1984 and the Star Trek episode 'Mirror Mirror' (the fascist parallel earth).
The Day the Earth Caught Fire.
It's a Wonderful Life.
John Wyndham's 'Random Quest'.
Conan Doyle's 'When the World Screams'.
La Donna e Mobile.
The Doctor : "I keep telling you, Brigade Leader, I don't exist here!"
Brigade Leader Lethbridge Stewart : "Then you won't feel the bullets when we shoot you."
The Doctor : "Listen to that! It's the sound of the planet screaming out its rage!"
Greg Sutton : "Marvellous, isn't it? The world's going up in flames and they're still playing at toy soldiers."
Brigadier Lethbridge-Stewart : ""Pompous, self-opinionated idiot," I think you said, Doctor."
The Doctor : "Yes, well, we don't want to bear a grudge for a few hasty words, do we? No, not after all the years that we've worked together. Now, come along, my dear fellow. Put on a smile..."
The Doctor : [Responding to Greg's less than enthusiastic impression of the TARDIS console] "What did you expect? Some kind of space rocket with Batman at the controls?"
The Doctor : "If you have a tool, it's stupid not to use it!"
"There's never been a bore like this one!"
The Doctor reveals that his normal pulse rate is 170 beats per minute. The TARDIS console can travel by itself, and is removable. [Perhaps this is what allows the Doctor to visit the parallel universe. The Doctor has had little if any experience of parallel universes before.]
The Fascists are led by a 'Big Brother' figure. [In the parallel universe an internal right wing revolution during World War II led to the appeasement of the Nazis.] It is implied that the royal family were executed. The Brigade Leader speaks of the 'Defence of the Republic Act, 1943'. The Party's slogan is 'Unity is Strength'. In their world Stahlman is Stahlmann.
The rifles used by the UNIT troops in the alternative universe are Soviet Simonov SKSs (forerunners of the Kalashnikov AK-47).
Stahlman's gas was a potential energy source found under the Earth's crust.
A top secret research establishment [an extra scene in the video version of episode five says the project is in Eastchester] and its 'fascist' equivalent, 23 July  (the desk calendar in the Brigade Leader's office shows 23 July - this is cut from the video release). The story takes place over five days. The Doctor is missing for nearly 48 hours from our world [but only 24 hours seem to pass on the parallel Earth according to the penetration count down].
The Doctor met [the future?] King Edward VII in Paris and states he was at Krakatoa during the eruption of 1883.
The story title, writer's credit and episode number captions for each episode are faded up and focused over a special stock footage montage of volcanic eruptions following the opening title sequence.
This story marks the last appearance in the series of the original TARDIS control console prop.
The primordial mutant creatures are named 'Primords' in the closing credits of the episodes in which they appear and in publicity material, but are unnamed in the story's dialogue.
Professor Stahlman's alter ego in the parallel universe at one point wears a radiation suit bearing a label on which his surname is prominently spelt 'Stahlmann' - although it is unclear whether this was an intentional indication of a further difference between the two universes or simply an error. He is named as 'Director Stahlman' in the closing credits to Episode 5, but this could itself be an error.
The 'parallel universe' aspect of the story was added to the scripts at the production team's suggestion to ensure that there was sufficient material to fill seven episodes. (This aspect of the story was present in writer Don Houghton's original outline; the aspect added to the scripts at the production team's suggestion was that of the Primord creatures.)
This was Caroline John's last story as Liz as she was pregnant and could not return for the following season. (Although it is true that the actress was pregnant, Barry Letts was unaware of this when he decided against renewing her contract.)
On the Nuclear Output Gauge in the Doctor's workshop, Megavolts is spelled 'Megga Volts'
Bessie travels with the Doctor and the TARDIS console into the parallel universe, despite the fact that it is ten feet away from them [It seems that only those elements that don't already exist on the fascist Earth are transported. Does a police box turn up at the Brigade Leader's HQ at the same time? The Doctor was never exiled to Earth in this world - it would hardly become his favourite planet - or he was killed soon after arriving.]
Liz, on the fascist Earth, in a kinky sub SS uniform and knee-length boots ('What are you doing in that ridiculous get up?' asks the Doctor).
Greg Sutton's patterned silk cravat.
The eye patch.
Cast & Crew
The Doctor - Jon Pertwee
Brigadier Lethbridge-Stewart - Nicholas Courtney
Liz Shaw - Caroline John
Bromley - Ian Fairbairn
Greg Sutton - Derek Newark
Harry Slocum - Walter Randall
Patterson - Keith James
Petra Williams/Dr. Petra Williams - Sheila Dunn
Primord - Dave Carter
Primord - Pat Gorman
Primord - Philip Ryan
Primord - Peter Thompson
Primord - Walter Henry
Private Latimer - David Simeon
Private Wyatt - Derek Ware
Professor Stahlman/Director Stahlman - Olaf Pooley
RSF Sentry - Roy Scammell
Sergeant Benton/Platoon Under Leader Benton - John Levene
Sir Keith Gold - Christopher Benjamin
Director - Douglas Camfield