The Sixth Doctor takes Evelyn on a trip to the prison colony island of Galapagos, to have dinner with a very young Charles Darwin. Six has done a bit of preparation to announce his presence, and is posing as a fellow scientist (well, as Albert Einstein) in order to make Darwin trust him.
Darwin is on the brink of making his big scientific breakthrough, and is formulating the final parts of his theory of evolution. He's having a major crisis of faith as well, since he believes in creation theory and is tremendously scared to lose his faith in the Bible. Evelyn and the Doctor gently coax him towards accepting his new theory, trying not too interfere too hard. They're rather rudely interrupted by a group of aquatic homo reptilians who believe they're the only survivors of their kind.
As it turns out, the Silurians have been busy hypnotising the island's staff and kidnapping Ecuadorian prisoners for their own purposes. One of the Silurians, a mad scientist, now plans to release deadly bacteria that will destroy mankind in one fell swoop and give Earth back to the Silurians. This scientist turns out to have created modern man from its ape ancestors as an experiment in the genetic modification of "cattle". And now he'd like to be worshiped as a new God. Humans, it seems, are nothing but a food experiment gone very, very wrong.
Darwin, predictably, gets a complete Heroic BSoD when he finds out about that, making him very susceptible to Silurian mind control. Luckily, he's able to focus on his faith and resists it — first by praying, then by realising his faith lies entirely in evolution theory and God has no meaning to him anymore. With some help (and a Heroic Sacrifice) from a Silurian ally, the Doctor manages to destroy the Silurian base and prevent the genocide of all humans on Earth.
Tropes:
- Artistic Licence – Biology: No, there is no missing link between Australopithecus and Homo sapiens, and there is no chance the former evolved directly into the latter — there are several intermediary forms between such as H. habilis and H. erectus.
- Artistic Licence – History: Darwin, though his views had changed somewhat by the time of his death, initially saw no conflict between his Christianity and the theory of natural selection, and his belief in a literal Garden of Eden tale is slightly anachronistic — until the rise of the fundamentalist movement some decades later, most mainstream Christians viewed the creation tale in Genesis as largely metaphorical.
- Clap Your Hands If You Believe: Charles' belief in natural selection over God allows him to break free of the mind control.
- Death by Irony: The planned death for Tulok, the genetic engineer, is to be exiled to the lifeless surface of the earth.
- Eyes Do Not Belong There:Emilio: "They are devils! Beings with three eyes!"
- Heroic Sacrifice: When the Doctor figures out the Myrka is tagged to track down Greta, she throws herself to it as to stop it's rampage.
- As well in the final confrontation with Tulok, Shvak throws up a psychic barrier between Charles and him, and succumbs to her wounds.
- Historical In-Joke: The reason why there isn't a Missing Link, despite you know..
- Humans Are Special: Alternately played straight and subverted in different ways throughout the story. Humans are naturally-evolved, a primate race, another branch of the great apes. No, wait, they're the results of Tulok's genetic engineering. But this makes them inherently susceptible to Silurian mind control. But Darwin posits that maybe, over thousands and millions of years, humanity has evolved enough to become their own organism, and have a chance to resist. By asserting their will and finding what they truly believe in, it seems that maybe he's right, and they manage to resist Tuvok's control. Then it turns out that no, actually, they're still powerless, and it was Shvak's psychic shielding that protected them all along.
- Hypno Pendulum: The Doctor uses a pocket watch to this effect.
- Indy Ploy: The Doctor's primary plan is to get to the main control room and come up with something "genius" on the way there.
- Lame Pun Reaction: "And that's something else, I tortoise." *groanz*
- More than Mind Control: One of the island officials voluntarily let himself be mind-controlled by the Silurians. The Doctor offers to undo the hypnosis, but the man will have to live with his own conscience and with the consequences of his actions. Terrified and wrecked with guilt, he chooses to stay hypnotised.
- Take That!: Evelyne thinks Melville (of Moby-Dick) is pompous and overblown. Like the Doctor.
- Telepathy
- Then Let Me Be Evil: Tulok seems to genuinely care about his creations, and despairs when they're released into the toxic surface world. Then it turns out that his "creations" are humans, and he deliberately raised them to sentience and intelligence, describing them as near his own people. This does not stop him from arranging the death of most of his entire race, and although he created humans, he has few issues wiping them out and reducing them to a food species once more.
- What the Hell Is That Accent?: the actor playing the Spanish-speaking Greta Rodríguez goes for a hysterical warble that sounds like she's about to fail an audition at the opera, and nothing like any Spanish-speaker anywhere, ever.
