Episode two, 7 February 1970
Episode three, 14 February 1970
Episode four, 21 February 1970
Episode five, 28 February 1970
Episode six, 7 March 1970
Episode seven, 14 March 1970
Written by Malcolm Hulke
Directed by Timothy Combe
Script editor: Terrance Dicks
Produced by Barry Letts
Jon Pertwee as the Doctor
Nicholas Courtney as Brigadier Lethbridge-Stewart
Caroline John as Dr Liz Shaw
Malcolm Hulke, the writer for "Doctor Who and the Silurians", was a mentor figure for Terrance Dicks, who had taken over as script editor midway through Patrick Troughton's final season. Dicks, of course, arrived at a time when the outgoing production partnership were planning a radical redesign of Doctor Who, for which "The Invasion" had been something of a test case.
That redesign was basically aimed at reducing the costs associated with producing Doctor Who. Time and space travel would be reduced from the programme, with the Doctor permanently anchored to present-day Earth. Stories would be extended in length, since it's easier and cheaper to produce a single eight-parter rather than two four-parters. And, with an eye on the upcoming switch to colour, the action component of the programme would be upped, to accomplish which a permanent supporting cast of military characters would be added.
When Dicks explained these format changes, Hulke summed them up instantly: "So you've got two possible plotlines to alternate between from now on. Mad scientists and alien invasions." Dicks thought about this for a minute, then realised, "Fuck me, you're right."
"The Silurians" is Hulke's first credit for the Pertwee Doctor, and, with the arrival of new producer Barry Letts, the start of the partnership between Letts and Dicks that would run the programme for all five years of Pertwee's tenure in the title role.
So far, the new format had produced two alien invasion stories and zero mad scientist stories. "The Silurians" is a third alien invasion story, but with a twist--the "aliens" are actually from Earth. They're a race of intelligent, technologically advanced reptile-men who ruled the planet during the time of the dinosaurs. Their scientists detected a large planetoid approaching the planet, the near miss of which would cause Earth to lose its atmosphere. In order to preserve their society, the Silurians put themselves into suspended animation, programming their computers to wake them up once Earth's atmosphere had returned. Except the computer never woke them up, because the atmosphere never "returned"--it was never wiped away in the first place. Instead of narrowly missing us, the planetoid got caught in Earth's gravity well and became our Moon.
Now, though, a colony of Silurians have been awakened, disturbed by the construction of a secret underground nuclear reactor in the Yorkshire moorland. Secretly aided by the construction project's chief scientist, they're drawing power from the nuclear reactor to aid in the resurrection of their race.
And you remember the other part of the reformatting, about the need to draw the stories out more? You know how the most traditional cliffhanger for the end of episode one of a Doctor Who story is a sudden, menacing reveal of what the monster looks like? "The Silurians" has that cliffhanger--at the end of part three. The story manages to go three full weeks before we get a good look at the alien race. For three weeks, there are rumours of monsters lurking in the cave systems--rumours of a monster roaming the moors--someone thinks they shot it, and it's wounded--people are turning up dead in barns and isolated cottages! It is, in fact, the middle of episode five before everyone is aware of the presence of the Silurians and on board with the threat they pose.
Those four and a half episodes are probably the story's strongest period. They're moody and creepy. It's only after that has all been milked for all it can give us that we move on to the direct confrontation between humans and Silurians, and this part of the story suffers from the fact that it's no longer possible to avoid putting the Silurians on the screen.
When the Silurians returned in New Who, opposite Matt Smith in 2010, their costuming was rightly criticised because it depicted anthropoid reptiles as having eyelashes, and anthropoid reptile females as having breasts. It's true that that sort of design choice is distracting, but trust me, it's not nearly as distracting as anthropoids where the rubber hood that's supposed to be their head is clearly waving and flapping around where it's supposed to be joined to the rest of their body.
Fortunately, this segment of the story proves much less amenable to elongation than the earlier portion. First, the Silurians release a virus into the human population, designed to cull the primate population. But it takes the Doctor only an episode and a half to find a cure, so the action returns to the nuclear reactor, where the Silurians take over the facility, inducing the Doctor to send the reactor into meltdown to keep it out of their hands. The Silurians flee the disaster by going back into hibernation, setting their machines to wake them again in fifty years; of course, as soon as they're safely gone, the Doctor averts the meltdown.
Which brings us to what's probably the most famous moment in "Doctor Who and the Silurians" (apart from when its title appears on the opening credits), the ending. The Doctor intends to reawaken the Silurians in a controlled environment, so he can reason with them and convince them they can cohabit with Earth's new inhabitants. The Brigadier consents to this plan. The Doctor and Liz leave to gather a team of scientists to study the Silurians, but as soon as they're gone, the Brigadier has the cave where they're hibernating blown up--he considers the threat they pose to humanity too great to take a risk on peace negotiations. This is, of course, the moment that's generally cited as when Doctor Who transitioned from a programme made for an audience of children to one made for an audience of young adults.
What Lisa thought
She has really taken to the Pertwee era so far--she finds it fun and a nice change of tone from the black and white era.
Of the two Jon Pertwee stories so far, this is the second one where Pertwee has found a reason to take his shirt off. This time, he strips down to what would now be called a muscle shirt (except that prior to Arnold Schwarzenegger, men didn't really have muscles), to demonstrate the extreme tension of the reactor meltdown sequence in episode seven.
And Lisa is ... impressed. We're talking about a fifty-year-old man from an era a whole decade before standards of male attractiveness had any sort of chiselledness to them at all, but Lisa still finds him rather fit.
She also liked seeing Geoffrey Palmer, whom she knows well as Lionel from As Time Goes By. Yup, he's here, experiencing the first in the series of violent, painful deaths he's going to undergo opposite Doctors ranging from Jon Pertwee to David Tennant.
So on we go. The next story will be "The Ambassadors of Death".