Young Silurian: This planet is ours!
Elder Silurian: This other species has developed its own civilisation. We must accept them as equals.
Young Silurian: I disagree! We must destroy them!
The Brigadier: You don't still think we can co-exist with the Silurians, do you?
The one where a grown man scribbles on the wall.
The Brigadier sends for the Doctor and Liz to take a look at an underground laboratory working on a new kind of nuclear reactor. They're getting odd power losses, a bizarrely high level of stress-related illnesses among the staff, and a background music composer with an inexplicable kazoo obsession.
The Doctor investigates while Liz spends most of the story just sort of standing there, and they discover that a neighbouring cave system is the base for a group of intelligent reptilian bipeds which are (inaccurately, as it turns out) named "Silurians" from the geological period from which they date. They have been in hibernation for millions of years, but the power and heat from the new reactor have reactivated them, and they now wish to emerge and reclaim "their" world from the mammals.
The Doctor tries to broker peace and gains the trust of the Silurian leader, but the leader's rebellious son takes power and releases a virus that will destroy humanity. The Doctor and Liz find a cure, but are then told that the Silurians have taken over the underground lab and are going to destroy the Van Allen Belt, bombarding the Earth with radiation deadly to mammals, but not reptiles. The Doctor gets them to retreat back into the caves by overloading the reactor and threatening an explosion. The Brigadier — to the Doctor's disgust — then orders the Silurian base destroyed.
Written by Malcolm Hulke. The only Doctor Who TV story to be officially titled "Doctor Who and...". Legend has it this was due to an error by the first-time director in having the script prefix added to the onscreen titles. (The title format stuck for the Target Doctor Who Novelisations, and was parodied by Big Finish Productions a few times.) While "Doctor Who" isn't his name, the actor was credited as playing "Dr Who" until 1970 and "Doctor Who" until 1981 (and again in 2005), so the Word of God on the subject is clearly a bit suspect. On another point of trivia, this was also the very last Doctor Who serial to be filmed in The '60s.
- Anti-Villain: Everyone aside from The Doctor, Liz and the Elder Silurian.
- Arbitrary Skepticism: The Brigadier scoffs at the Doctor when he first tells him that there are intelligent reptilian beings living in the caves. Yeah, as if that's any weirder than robotic yetis, alien cyborgs and living plastic mannequins...
- Asshole Victim: Doctor Quinn, Major Baker.
- Cat Scare: A chicken jumps out as a UNIT squad searches the barn for the escaped Silurian.
- Character Name and the Noun Phrase: The only one (not counting Six' awesomely silly Big Finish story "Doctor Who and the Pirates, or The Lass That Lost A Sailor"), due to an error in the script department.
- Creator Cameo: Assistant script editor Trevor Ray is the ticket collector and Barry Letts and Terrance Dicks are passengers.
- Darker and Edgier: Between the moral ambiguity, extremely depressing ending and biological horror this could easily pass for a Torchwood story.
- Doomsday Device: The Younger Silurian intended to use a weapon to destroy the Van Allen Belt and make the Earth's environment hostile to humankind
- Downer Ending: After the Doctor suffered a tense back-and-forth struggle to make the Silurians cool their jets upon awakening to the new dominant species and attempting to broker peace between the humans and Silurians, one of the younger Silurians said no to the whole idea, then took over by force and started an invasion. As a result, the Brig blew up the whole cache of Silurians, lock, stock and barrel. Needless to say, it made the Doctor REALLY angry.
- Everything's Better with Dinosaurs: The Silurians have a pet Tyrannosaurus or whatever.
- Evil Army: Both the Silurians and humans have this trope
- Evil Counterpart: The Young Silurian to The Brigadier. Both rebel against more level headed elders vying for peace, both show extreme courage and determination when their respective races are threatened and both are utterly prepared to wipe out the other party to ensure that their people survive. However, this trope is arguably subverted, as neither one is truly more evil than the other, and while the Young Silurian is foiled the Brigadier's orders to have the Silurians wiped out go off without a hitch.
- Fantastic Racism: The Silurians frequently refer to the humans as "apes", and they treat humans as a lesser species. The Humans feel the same way about the Silurians.
- Freak Out!: Peter Miles gives a truly amazing one, going from Creepy Monotone to ham in .01 seconds.
- Genocide Dilemma: An unusual mutual example
- Grey and Gray Morality: Except for the Doctor and Liz - and perhaps the Elder Silurian - nobody comes out looking particularly good in this story, not even the Brigadier. Most characters on both sides retain sympathetic qualities, however. This sort of complexity - that people in general aren't good or bad - was a staple of Malcolm Hulke's scripts - he was also involved in writing "The War Games" a story dealing with Deliberate Values Dissonance.
- Humans Are the Real Monsters / Non Humans From Earth Are Pretty Nasty As Well
- Humans Are Flawed: It's played on both ends of the spectrum, too - the Silurians are just as xenophobic as their human counterparts, and yet neither side completely loses all sympathy when all their actions are examined in hindsight.
- Then again the Elder Silurian is probably the only thoroughly good character in the story other than Liz and the Doctor.
- Kill All Humans: What the more unreasonable Silurians would like to do.
- Klingon Promotion: There's no hint that any other Silurians have a problem with the Young Silurian straight-up murdering the old leader and taking his position.
- Lizard Folk: The Silurians, with vaguely piscine features.
- Names to Run Away from Really Fast: For viewers only familiar with later stories, the name of one of the characters can be foreboding... but this story's Frederick "Freddie" Masters has nothing to do with the Doctor's arch-enemy the Master. In fact, Frederick Masters is killed by the Silurian virus.
- People in Rubber Suits: Leading to Special Effects Failure due to their conspicuously wobbly heads.
- The Plague: Unleashed on humanity by the Young Silurian in Part 5. Very clearly stated to be bacteria-based, however, rather than a virus.
- Properly Paranoid: The Humans and Silurians both believe the other side is trying to wipe them out. They're both right. Mainly because they're also trying to wipe them out.
- Similar Squad: The Doctor, Liz, and the Brigadier when compared to the Elder Silurian, Silurian Scientist, and Young Silurian respectively.
- Shoot the Dog
- Shout-Out: The Doctor sings The Jabberwocky.
- Synthetic Plague: The Young Silurian releases a plague in an attempt to destroy humanity.
- Third Eye: The Silurians can project some kind of invisible beam from their third eyes to kill humans and each other.
- Vague Age: Even the Doctor can't get his age straight:I'm beginning to lose confidence for the first time in my life - and that covers several thousand years.
- What Measure Is a Non-Human?: Averted. The Doctor wants peace with the Silurians and is very upset with the resolution.
- What the Hell, Hero? - The Brigadier ordering the Silurian compound destroyed at the end, wiping out the colony. After the explosion, the Doctor drives away with a disgusted look on his face. Because hey, it's not like the Elder Silurian had been murdered by his warmongering son, or that the Silurians had barely been stopped from destroying all Human life on Earth not once but twice - no, wait, that's EXACTLY how it was. What The Hell Doctor?
- Because he's not just disgusted at the Brigadier. Neither species of Earthling impressed him today.