The one where a man becomes a killer cotton ball.
Three dudes, one of whom is a security agent for the Second Great and Bountiful Human Empire, crash in a jungle. They discover a Dalek plot to take over the solar system, and all end up very dead. Shades of James Bond abound.
An animated reconstruction exists, made by fan animators, and partly funded by well-known 80s superfan Ian Levine.
The serial was recreated in live action in 2019 by students of the University of Central Lancashire; the recreation had the full support of the BBC. It's likely the only such recreation that could ever be feasibly made, given the story's unusually short nature (only being superseded [subseded?] by the mini-episodes of the revival series) and lack of any of the show's principal cast. It premiered on the official YouTube channel for Doctor Who on October 9, 2019, exactly 54 years after the original episode was broadcast. It can be seen here.
This episode/story provides examples of:
- Absentee Actor: The Doctor and his companions don't appear at all.
- Backdoor Pilot: After "Planet Of Giants" was shortened and a hole in the schedule was created, Terry Nation wrote this episode partially as a teaser for the upcoming "The Daleks' Master Plan" and partially to see if a Dalek spin-off show could work. (It could, but not until much later and in some entirely different media.)
- The Bad Guy Wins: Cory never stood a chance.
- Body Horror: The Varga plants. Used as watchdogs by the Daleks, these are giant ambulatory cacti with at least a basic animal-like intelligence. They hunt animals - any animals, including humans - and then shoot their spines into them. These spines carry a venom with unusual effects: the victim first becomes paranoid and psychotic, obsessed with killing; then, they transform into Varga Plants themselves. Even killing the host body does not arrest the transformation. Brrrrr.
- Bottle Episode: This episode was written hastily when the final two episodes of "Planet of Giants" were re-edited into one, creating a one-episode gap at the end of the season. It uses three sets (a human spaceship, the Dalek War Room and a jungle) all built for and recycled in "The Daleks' Master Plan", a couple of Daleks, a couple of very low budget monster suits made of glue and fluff representing Plant Aliens (which also get reused in "The Daleks' Master Plan"), a bunch of rather better-looking aliens on the Dalek ship (also reused in "The Daleks' Master Plan") and a spot of cheap Gorn. There is no Doctor, no companions, and the majority of the episode takes place with two actors arguing in the jungle.
- Chromosome Casting: There are no female characters whatsoever. Just men, male aliens and Daleks. (Except maybe Sentreal. We're not quite sure what Sentreal is). The only Doctor Who story ever made to hold such a distinction, barring "The Deadly Assassin" which features a female voiceover part in one episode (as the voice of a computer) but is otherwise all-male.
- Exactly What It Says on the Tin: The episode's alternate title in production was "Dalek Cutaway", which tells you exactly what you're getting. This alternate title was often listed along with or in place of "Mission To The Unknown" as the title of the episode for years until some of the disputed episode titles were standardised.
- Expy: Terry Nation devised Marc Cory as "a space-age James Bond".
- Family-Unfriendly Violence: Lowery gets a three-inch thorn jabbed graphically through his hand, which is going to cause him to transform into a homicidal plant zombie.
- Kill 'Em All: Everyone dies except the Dalek and the mysterious council of aliens (all of which die in "The Daleks' Master Plan" later). Everyone means everyone - the Doctor and his companions don't show up in this episode at all, and so are spared.
- Lower-Deck Episode: The protagonist is Marc Cory in the absence of the Doctor and his companions.
- Mauve Shirt: Marc Cory.
- Out-of-Genre Experience: This is a one-parter (at a time when serials were the norm) Bottle Episode which is still unique in not having either the Doctor or any of the companions in it - it's a kind of extreme Lower-Deck Episode with just victims and Daleks. This had a reason behind it.
- Plant Aliens: The Varga plants homicidal mobile plants which infect people, first making them turn into homicidal maniacs, and then into Varga plants. And they are native to Skaro, which suggests that they might be another of Davros' projects.
- Poorly Disguised Pilot: This was an attempt at pitching a spin-off Dalek Space Opera series for an American audience, and so the episode focuses on members of an anti-Dalek military force as well as establishing the Daleks in alliance with a bunch of never-seen-before alien species (which also all had silly voices and outrageous designs, for Toyetic reasons). A pilot for this series was written, but never made, although Big Finish recorded an audio adaptation of it, and some of the ideas wormed their way into Blake's 7 later on.
- Red Shirt: Jeff Garvey and Gordon Lowery are infected with Varga thorns and killed by Cory.
- Sci-Fi Writers Have No Sense of Scale: The script uses the terms "solar system," "galaxy" and "universe" interchangeably.
- Sequel Hook: For "The Daleks' Master Plan".
- Sliding Scale of Anthropomorphism: The delegates provide some nice examples. Two are Human Aliens, three are Rubber-Forehead Aliens, and Sentreal is a Starfish Alien.
- Took a Level in Badass: The Daleks, and the whole point of this story. After three defeats at the hands of the Doctor, the latter of which went out of its way to portray them as incompetent buffoons, how do you make the Daleks scary again? Put them up against James Bond and have Bond lose!
- Transflormation: Varga Plants, the thorns of which contain poison that transforms victims into other Varga Plants.
- The Virus: Varga plants.
- Zombie Infectee: Lowery doesn't admit to Cory that he's been envenomated by a Varga thorn until he's on the brink of going homicidal and his involuntary murmuring of "kill" gives him away.