The one with a killer phone cable and the first appearance of an iconic villain.
Although a theme that had been explored before, with the Meddling Monk ("The Time Meddler") and the War Chief ("The War Games"), the introduction of the Master as the main villain for every story of season 8 saw a true Evil Counterpart for the Doctor — a Moriarty to the Doctor's Sherlock Holmes, as the BBC Classics website puts it. Roger Delgado played his first known incarnation, yet not the first chronologically like William Hartnell but that's a story for another time. It was also the debut of Josephine "Jo" Grant (Katy Manning), and Captain Mike Yates (Richard Franklin), both of whom would go on to have very prolific careers in the Big Finish audio range after their classic series runs.
The Master lands his TARDIS (which does have a working chameleon circuit) in a circus, and sets about his evil plan; first he steals a Nestene energy unit from a museum (see "Spearhead From Space"), then reactivates it using a radio telescope and finally takes over a small plastics firm using his powers of hypnotism. Using the firm's factory, he produces deadly chairs that engulf and kill, plastic daffodils that spray a plastic film over the mouth and nose, and deadly plastic dolls. Autons distribute the daffodils in a promotional campaign. The final phase will be to use the radio telescope to summon the Nestene Consciousness and activate the daffodils.
Meanwhile, the Doctor is investigating the mysterious deaths caused by the chairs and dolls with the help of Jo Grant, a young UNIT assistant who has been given her position thanks to a uniquely persistent relative. Jo falls under the Master's hypnotic influence and nearly blows up UNIT HQ with a bomb. Later, the Master installs a new telephone in UNIT HQ and the cord nearly strangles the Doctor.
Eventually, though, the Doctor persuades the Master that the Nestene Consciousness will have no use for him once they arrive, and they work together to repel the Consciousness into space.
After the Master pulls off a last-minute escape from UNIT troops, the Doctor notes that they are unlikely to have heard the last of him, and that actually he's quite looking forward to matching wits with him again.
- Arm Cannon: The Autons.
- Artistic Licence - Multiple Sciences: The plastic film that's used to smother people is dissolved by carbon dioxide, even in the low concentration of normal breath. Even ignoring just how carbon dioxide could dissolve plastic, it should dissolve while people are choking, as all of the oxygen in their lungs is being converted into carbon dioxide. That way, the film would release its victims before it could kill them. Possibly excusable if there's a time-delay between the film's release and its becoming vulnerable to breath.
- Ironically, if you think about it, it might prove Liz Shaw's point from Spearhead From Space - that despite it being like plastic, it isn't.
- Art Imitates Art: The Time Lord's appearance hovering in mid-air is a Shout Out to Rene Magritte's painting Golconda, showing similarly-dressed men falling like rain.
- Attack of the Killer Whatever: The story has killer inflatable chairs, killer plastic daffodils, killer Brand X Troll-dolls, killer advertising eyesores... Robert Holmes cited his inspirations for the story as the preponderance of cheap disposable plastic fad items that began to really take off in the '70s, and realising you would only need four inches square of plastic sheet to suffocate someone.
- Badass in a Nice Suit: The Master dons a suit with an orange tie to disguise himself as a businessman, and arguably spends more time in disguise than in his Nehru jacket attire in his debut. If you can't already tell, the Master of Disguise act will become his trademark. He is a "Master", after all.
- BBC Quarry: For once, it isn't doubling as an alien planet.
- Black Comedy: Goodge gets crushed to death and left by the Master for the Doctor to find, in his own lunchbox. McDermott is eaten by a suspiciously warm inflatable chair. The Master has a friendly phone conversation with the Doctor and then tries to murder him by sending a signal down the telephone that makes its cord wrap around the Doctor and start crushing him. 40,000 people are suffocated by daffodils. The Master's Complexity Addiction is played completely for laughs. It's one of the funniest stories of the original series ever, and was also so nasty that Barry Letts had to publicly apologise and promise the Moral Guardians that he'd never make anything like that again.
- Given the events of the previous serial, you'd think the Doctor would stay clear of singing a song that has the line "I don't want to set the world on fire"...
- Breaking the Fourth Wall: An Auton hands a daffodil directly to the camera.
- Characterization Marches On: Jo karate-chopping Benton — her character was originally envisioned as an Emma Peel-Expy.
- Chromosome Casting: Aside from Jo, Mrs. Farrell is the only female character in the story.
- Complexity Addiction: The Doctor notes that the Master's preferred murder methods are "vicious, complicated and inefficient - typical of your way of thinking."
- Continuity Nod: The Doctor tells Jo that Captain Yates had the job of clearing up the mess caused by the Autons during their previous invasion.
- Corporate Conspiracy: The Master uses his hypnotic abilities to take over Farrel Autoplastics, using it to make products that can be controlled by the Nestene in his master plan to summon them back to Earth.
- Decoy Getaway: The Master hypnotises Rex Farrel, dresses Farrel in his clothing and a Latex Perfection Roger Delgado mask, and sends him out to do a Suicide By UNIT. While the Doctor and UNIT are distracted, the real Master slips away.
- Desperate Object Catch: How the Doctor disarms the Volataliser booby trap.
- Early Instalment Weirdness: The Time Lord representative wearing a bowler and three piece suit, when we'll later see Time Lords traditionally dress in ornate robes with odd hats. However he states that he's trying to blend in "unlike some". However, the ability to effortlessly float in mid-air under his own power he demonstrates is something no other Time Lord does, except the Tenth Doctor under very unique circumstances. note Possibly justified if he was a projection or using an invisible TARDIS (since he does appear and disappear with the classic wheezing, groaning noise).
- Education Through Pyrotechnics: The Meet Cute between the Doctor and Jo Grant. The Doctor is singing "I don't want to set the world on fire..." when his equipment blows up, producing copious amounts of smoke. Jo grabs a fire extinguisher and douses the laboratory bench, only to get shouted at by the Doctor for ruining three months of work.
- Establishing Character Moment:
- The Master's first scene establishes him nicely.
- Jo is introduced barging in on the Doctor's experiment and accidentally causing it to explode by trying to be helpful.
- Everyone Knows Morse: While the Doctor is tied up on the floor of the Autons' bus, he manages to reach the brake pedal with his foot and manages to send a (surprisingly long and detailed) morse message to UNIT, who he knows have the bus under observation.
- Fake Shemp: Nicholas Courtney suffered a sudden illness an attack of depression during filming, so his dialogue was re-written to reduce the Brigadier's involvement. A double stood in for Courtney on location, with filming arranged so the Brigadier was either seen only from behind, obscured by another character or strategically out of camera shot. (There is a scene in the finished programme where Courtney's double is clearly shown to be wearing non-military white socks.) Fortunately, Courtney was able to return to filming within a few days.
- Family-Unfriendly Violence: Jo gets blasted in the face by a Nestene plastic daffodil that seals her mouth and nose under a few inches of plastic, instantly glued to her face. Her look of horror as the Doctor tries to pull it off, can't, and dashes away to get help is stomach-churning. The Doctor rescues her by spraying her with acetone. Considering the serial was inspired at least partially about warnings about plastic bags, this had elements of Some Anvils Need to Be Dropped about it.
- Fauxreigner: The circus director goes by the name "Luigi Rossini", and to begin with he addresses the Master in English with an Italian-esque accent. But when the Master reveals that he just happens to know that the director's real name is the very English-sounding "Lew Russell", the surprised director switches to a broad London accent.
- Gonk: That troll doll.
- Latex Perfection: The Master's disguise masks. Possibly justified as Auton tech.
- Long Bus Trip: Liz Shaw has departed between seasons, and is said to have returned to Cambridge after telling the Brigadier that the Doctor didn't need a lab assistant, he just needed someone to pass him his test tubes and tell him how brilliant he was.
- The Master: For the very first time.
- Moral Guardians: this story caused one of the biggest violence/horror controversies in the show's history. In particular, it was claimed that the ep 2 cliffhanger with the Auton policemen would make children fear and distrust the police, and that the murderous troll doll had left children scared that their cuddly toys would strangle them in their sleep. Barry Letts has said that the reaction did convince him that they'd gone overboard, and to self-censor more in later seasons.
- Mouth of Sauron: A Time Lord travels 29,000 light years to warn the Doctor the Master has come to Earth, though his coordinates slipping means he appears in mid-air.
- Nepotism: Jo gets into a position she really isn't qualified for thanks to a connected relative.
- No Ontological Inertia. Played straight. The Master awakens a dormant meteorite containing the Nestene Consciousness, which animates a group of Autons (plastic automata) he created, which go on to create second-generation Autons that also come alive with the Nestene Consciousness. When the Autons take care of the first phase of the invasion, the Master uses a radio telescope to broadcast some kind of energy that allows a Nestene mothership to instantly materialize in Earth's sky. When the Doctor reverses the polarity of the telescope, not only does the mothership disappear, but every Auton falls lifelessly to the ground. Justified in that the Autons are not independently intelligent, but are directly controlled by the Nestene Consciousness.
- No Pronunciation Guide: The Doctor pronounced the word Cephalopod "Kephalopod."
- Not Himself
- Not My Driver: The cliffhanger to Part 2 has the Dramatic Unmask of an Auton posing as the Doctor and Jo's cab driver just long enough to kidnap them and lead them to an Auton ambush.
- Obstructive Bureaucrat: Played with. The Doctor instinctively treats Brownrose as one, even though he's actually being quite helpful.
- Our Monsters Are Weird: The Master has murderous plastic daffodil monsters and an inflatable chair that eats people.
- Real Life Writes the Plot: Nicholas Courtney suffered a sudden illness - an attack of depression - during filming, so his dialogue was re-written to reduce the Brigadier's involvement. However, Courtney was able to return to filming within a few days.
- Reverse Polarity: The Doctor does this in order to make the thingamajig do somethingsomething so that the Nestene will return to space.
- Rogue Agent: The Master is a rogue Time Lord, so it makes sense for the Time Lords to use another rogue Time Lord, the Doctor, to stop him.
- Second-Face Smoke: Circus owner Rossini blows cigar smoke in the Doctor's face.
- Sequel Episode: To Spearhead from Space.
- Somebody Else's Problem: The Time Lords know how dangerous the Master is, so they just let the Doctor know he's in the area and proceed not to give him any help at all.
- Stuffed into the Fridge: The Master kills a scientist by shrinking him, and then makes a point of stuffing the tiny body in the scientist's lunchbox for the Doctor to find later.
- Tied Up on the Phone: a telephone cord is actually an agent for the Autons and tangles up the Doctor.
- Twisted Ankle: Jo hurts her ankle escaping from a moving vehicle in the last episode, though it doesn't slow her down for long.
- Ungrateful Bastard: When Jo rescues the Doctor from the Master's caravan, he chastises her for not staying put. Not even a "thank you".
- Villain: Exit, Stage Left: UNIT do chase after the Master, but give up when they find his abandoned vehicle. The Doctor is completely unconcerned about the likelihood of the villain returning. "As a matter of fact, Jo, I'm rather looking forward to it."
- When Props Attack: All the Auton-possessed object scenes have huge amounts of this, but especially the doll sequence.
- Worthy Opponent: The Master calls The Doctor and previous adversaries this in part four.