The one where Jamie slaps Polly.
The Doctor, with Polly, Ben and Jamie in tow, lands the TARDIS on a volcanic island where they are captured and taken into a cave complex. It soon becomes clear that this tiny island is all that remains of the ancient Atlantean civilisation.
Mad scientist Professor Zaroff (played with a Large Ham by Joseph Furst) has convinced the Atlanteans that he can raise the city from the sea, but in reality he plans to drain the ocean into the Earth's core and thereby destroy the planet. Just because, OK?
Polly is taken off to be converted into an aquatic Fish Person, while the others meet two shipwrecked sailors who help them convince the Fish People to rebel. Eventually, the Doctor manages to foil Zaroff's plan by flooding the city before he can complete the drilling. Zaroff drowns, but everyone else makes it out and the Doctor and companions depart.
For a long time it was thought that only episode 3 remained, until episode 2 turned up in 2011. They are the earliest Troughton episodes known to exist, as his first two serials remain lost in their entirety.
- Actually Pretty Funny: Zaroff is only very briefly angry when he learns that the Doctor tricked him into saving his life with a blatant lie.
- Adaptation Expansion: The novelization gives a deeper motivation for Zaroff's scheme-his wife and daughter died in an accident, and he can't stand the thought of the world going on without them.
- Adorkable: The Doctor practically vibrates with glee when Ramo offers him his people's ceremonial robes and bizarre headdress as a disguise, then looks a little sheepish at his own excitement.
- Atlantis: Or at least the last remnants of that civilisation, living underground.
- Author Filibuster: Against organised religion in part 4.
- Big Bad: Professor Zaroff.
- Body Horror: Polly almost has surgery to turn her into a fish-person.
- Bottle Episode: It was an unpopular script that was dashed out as cheaply as possible when the producers realized it was the best script out of the bad bunch they had. Unlike other examples, this does not work in the episode's favour as it relies very heavily on sets (representing a massive Atlantean temple system with a series of box rooms with shells glued on), costumes (cardboard headdresses for everyone!) and monsters (the 'fish people' are dressed in what look like Pierrot-style white ruffled bodysuits with sequins to represent scales and big cardboard eyes). Some people find this to be enjoyable 1960s camp and link it to the psychedelia movement. Others find it Special Effect Failure.
- Broken Aesop: As noted, the Author Filibuster has the Atlanteans blame their religion for all their problems. Even though the actual culprit Zaroff didn't seem to have much of anything to do with their religion. Or that one of the few Atlanteans to see through Zaroff's deceptions and distrust him (even before the Doctor's help) was one of the priests of their religion. And the character making the Filibuster had been an antagonist who hadn't done anything good, sympathetic, or redemptive up to this point. The Filibuster was apparently supposed to be that character's redemption.
- Also, the prophecy did come true in a way.
- Chewing the Scenery: Zaroff was a fandom injoke for how much he milks the line "NOTHINK IN ZE VORLD CAN SHTOP ME NOW!!", which is used as The Stinger at the end of the official DVD trailer. And, of course, "BANG! BANG BANG!"
- Chickification: This story is particularly extreme in depicting Polly as a Distressed Damsel with no redeeming moments of agency, to the displeasure of the actor Anneke Wills.
- Cyborg: The fish-people, humans fitted with 'plastic gills' and artificial eyes that allow them to see better underwater.
- Dare to Be Badass: Sean uses this approach to persuade the Fish People to go on strike.
- Didn't Think This Through: Zarvoffs face when the Doctor actually asks him why he intends to blow up the world makes it clear that the question had simply never occurred to him before.
- Dressed All in Rubber: Zaroff's thugs (and while impersonating them Ben and Jamie) wear rubber wetsuits.
- Earth-Shattering Kaboom: What Zaroff hopes to create.
- Evil Is Hammy: Zaroff could have a Ham-to-Ham Combat with the Daleks and have a good chance of winning. He's so shouty, mad-eyed and completely over-the-top that it keys off the Doctor into knowing he's Obviously Evil long before anyone else has figured it out. And no-one else seems to understand this, much to the Doctor's confusion.
- Family-Unfriendly Violence: A surviving clip from episode one shows Polly being forcibly anaesthetised in preparation for being turned into a fish-person while screaming and bellowing in protest.
- Fish People: Created by surgery rather than a natural species. Polly almost becomes one in some of the few clips to survive from episode 1 and in the newly-recovered episode 2.
- For SCIENCE!: The closest Zaroff comes to an explanation of his motives in the TV story (but see the All There In The Manual entry above) is pretty much this.The Doctor: Just one small question. Why do you want to blow up the world?Zaroff: Why? You, a scientist, ask me why? The achievement, my dear Doctor. The destruction of the world. The scientist's dream of supreme power!
- For the Evulz: Zaroff tries to destroy Earth just for the fun of it.
- Get a Hold of Yourself, Woman!: The now-infamous scene of Jamie slapping Polly to snap her out of a mental breakdown; the bit was originally written with the more overtly chauvinistic Ben in mind before Jamie was unexpectedly added to the regular cast.
- God Guise: Ben prevents the execution of the Doctor and Ramo by speaking from inside the hollow idol of Ando and pretending to be the voice of the goddess.
- Human Sacrifice: The Atlanteans try to sacrifice the Doctor and company to the goddess Ando... using sharks.
- I Can't Believe I'm Saying This:Jamie McCrimmon: You know I never thought I'd say this, but well it's great.
- La Résistance
- Mad Scientist: Zaroff is a classic example.
- At the end of the Episode 2 clip on the BBC site, he sounds like a proto-Davros, on how succeeding with his omnicidal mania would be the ultimate power.
- Made a Slave: The Atlanteans enslave all outsiders who stumble on their land, except for Zaroff.
- Obscured Special Effects: The Knockout Gas used by the Atlanteans is invisible.
- Ominous Latin Chanting: The Atlantean cult chant ominously in a gibberish language ("waa-aa-tuu-aah waa-aa-tuu-aah Wah! Wah! Wah!") while performing religious rituals (like chaining the Doctor and his companions on top of a shark pit). It is combined on the soundtrack with dissonant electronic hits and a creepy organ.
- Out-of-Character Moment: There's a scene where Polly is trapped in a flooding chamber and panicking and screaming that she can't do it, and Jamie pulls her to her feet and slaps her on the face. This was in a Missing Episode, and when The BBC's narrated audio reconstruction was made, Anneke Wills and the director both agreed that Jamie didn't slap Polly because it didn't fit his character or their relationship, and they felt that Jamie dragging Polly to her feet would have been enough to snap her out of it.
- Religion Is Wrong: The conclusion the surviving Atlanteans reach through dubious means at the end.
- Strapped to an Operating Table: Polly, to be turned into a Fish Person. The scene is disturbing enough to have been cut in Australia and to have provoked protests from Moral Guardians that it would make children frightened of doctors.
- Suicidal Cosmic Temper Tantrum: Zaroff.
- What the Hell Is That Accent?: It's Joseph Furst's real one, that's what.