Harrison Chase: "What do you do for an encore, Doctor?"
The Doctor: "I win."
"You and your kind are nothing but parasites. You're dependent upon us for the air you breathe and the food you eat. We have only one use for you..."The TARDIS arrives in England as two large alien seed-pods are found in the Antarctic permafrost. Helicoptered out to the Antarctic base to see for himself, the Doctor identifies them as Krynoids: a particularly rapacious plant that will, if allowed to germinate, consume all life on Earth.One of the scientists, Winlett, is infected by the pod and begins to turn into a Krynoid himself. But he's destroyed by a bomb set by a mercenary, Scorby, and a rather confused botanist, Keeler, who steal the other pod on behalf of their employer, plant collector (and nutjob) Harrison Chase. Chase takes Sarah hostage and plans to open the pod in her presence, which will infect her. The Doctor rescues Sarah, and Keeler, who genuinely never wanted to get caught up in a murder case, ends up infected. This doesn't bother Chase much, and he begins to feed Keeler raw meat to accelerate the transformation. At this point, people start calling UNIT, but the Brig is in Geneva and his replacement isn't really the quick type.The Keelernoid grows bigger and bigger, eventually beginning to take over Chase's mansion, while the mad collector decides to turn the Doctor into compost to feed it. But he ends up falling into the crusher himself, while the Krynoid is bombed by the RAF.Not to be confused with "The Seeds of Death".
— The Krynoid, speaking through Harrison Chase
- Alien Kudzu: The Krynoids, which can possess Earth plants.
- Amputation Stops Spread: After Winlett is infected by the Kyrnoid, the team plans to amputate his arm in the hope that it would maybe slow the infection while they think of something else to try. However, the Kyrnoid takes him over and he escapes before they can do so.
- Art Shift: Third of four Tom Baker episodes which use video rather than film for location shooting; as with "Robot", this was to accommodate the visual effects used in Parts 5 and 6.
- Applied Phlebotinum: Military-grade weed killer. The Doctor used it to get Sarah Jane and Scorby out of a jam...and then ran out of it.
- Attack of the 50-Foot Whatever: Plant, in this case.
- Badass Boast: After the Doctor dramatically leaps through a skylight to rescue Sarah:Chase: What do you do for an encore, Doctor?
(The Doctor grins that shit-eating grin of his.)
The Doctor: I win!
- Batman Grabs a Gun: For once the Doctor advises a military solution.
- Also literally at one point as he swipes Scorby's handgun, but never actually uses it, intending just to threaten with it.
- BBC Quarry: As Antarctica with a white paint job. A different part of the same quarry was then used as an actual quarry for the fight scene between the Doctor and Chase's chauffeur.
- Beard of Evil: Scorby.
- Berserk Button & Beware the Nice Ones: Folks, we're used to Four smiling a goofy smile, all teeth and curls. We have never truly seen him PISSED. THE FUCK. OFF. Until now. While The Sontaran Experiment gave us only a glimpse of it, this is the first of at least two times in Four's tenure where we see what happens when you set him off. And if you can piss off the Fourth Doctor, you're a rare breed. Or a moron.
- Big Bad: Harrison Chase.
- Body Horror: There's no other way to describe the Krynoid transformation.
- Bond Villain Stupidity: Scorby, all the time.
- Brandishment Bluff: The Doctor pilfers Scorby's gun. When Sarah points out he'd never actually use it, the Doctor replies, "They don't know that."
- Changed My Jumper: At the end of the story, Sarah Jane Smith ends up walking out into Antarctica — in a swimsuit due to a TARDIS error.
- Conspicuous Gloves: Chase almost always wears black leather gloves, except when meditating in his greenhouse. According to the Novelization and the DVD commentary, this is because Chase Doesn't Like Being Touched, at least not by his fellow humans.
- Conveyor Belt-O-Doom: Leading into Chase's compost machine. The Doctor, Sarah Jane, Sergeant Henderson and finally Chase all end up on it at one time or another.
- Cool Old Lady: Amelia is thrilled by the idea of infiltrating a maniac's mansion.
- Doesn't Like Guns: When Sarah Jane sees the Doctor packing a pistol, she points out he'd never actually use it and he agrees.
- Doomy Dooms of Doom
- Dressing as the Enemy: The Doctor gains entry to Chase's mansion by stealing the hat and coat of the limo driver who tried to kill him and just driving through the front gate. Once he actually gets out of the car and the guards realize he's not the regular driver, the disguise fails. Hilarity Ensues.
- Enemy Mine:The Doctor: Can I rely on you, Scorby?Scorby: For the moment, Doctor.
- Evil Is Not a Toy
- The Extremist Was Right: Scorby suggests bombing the Krynoid at one point but the Doctor shoots him down, saying that nothing they have to hand would create a powerful enough explosion. Cut to a few episodes later, and the RAF provides just such an explosion.
- Fate Worse Than Death: "It's more serious than death, Mr. Stevenson. He's changing form."
- For Science!: Chase's original motivation until the Krynoid possessed him.
- Frickin' Laser Beams: UNIT now has rather clunky and homemade-looking laser guns. It still does little more than annoy.
- Garden of Evil: Chase's estate is turned into one of these as all the flora falls under the control of the Krynoid.
- Genre Savvy: The Doctor, overlapping with Danger Deadpan as usual. When Chase says he's going to kill him, Sarah protests, but the Doctor simply points out that, as the villain, Chase has to kill them; "We keep interfering!" he observes. The Doctor's insight and honesty suitably impress Chase.
- Gory Discretion Shot: When Chase is composted, all we get to see is the Doctor looking away in disgust.
- Halfway Plot Switch: Well, one-thirdway at least. We get a two-part story in the Antarctic base, followed by a four-parter in Chase's mansion.
- Hoist by His Own Petard: Chase falls victim to the compost machine, which he'd used earlier as a murder weapon.
- "I Know You're in There Somewhere" Fight: Averted by the first Krynoid, as the Doctor makes it clear that Winlett's consciousness was destroyed at a relatively early stage of the infection. Subverted by the second Krynoid, as it's revealed that the Krynoid did keep some of Keeler's personality... but only enough to enable it to speak English.
- Immune to Bullets: Averted; for once the Doctor recommends dealing with a menace via military means... and the Brigadier isn't there to see it. But played straight in that any weapon, short of missiles, doesn't affect the Krynoid.
- Insistent Terminology: After Winlett fully transforms into an early-stage Krynoid, the Doctor flips out whenever anyone refers to it as "Winlett" rather than "the Krynoid," likely because of the danger of someone hesitating to kill the Krynoid in the vain hope that Winlett can somehow be restored.
- Hypocritically, he keeps calling Keeler by his name, even when he transformed into an eight foot tall plant that no longer even resembled a human.
- It Is Pronounced Tropay: Miss Ducat insist her name be pronounced Du-cah.
- It Can Think: At first we believe the Krynoid to be an instinctual, mindless creature. But then it tries to bargain with the Doctor in Keeler's voice...
- Janitor Impersonation Infiltration: The Doctor disguises himself as a chauffeur to sneak into a mansion, an odd moment since his usual bluffing tactic is being commanding and having charisma for miles. It convinces no-one - perhaps because of this, or perhaps because he was clearly still wearing his scarf under his coat.
- Karmic Death: Chase ends up shredded in his own human compost machine, after trying to drag the Doctor in. While the Doctor was trying to save him.
- Kill Us Both: The Doctor ends the story by calling in an air strike on a building he's trapped in, due to the danger of the Krynoid releasing its seeds all over the planet. He gets out in time.
- Literal-Minded:Scorby: Get your hands up. Turn around, Doctor.
(The Doctor does a full 360 turn.)
Scorby: Facing this way.
The Doctor: Have we annoyed you or something?
Scorby: Shut up. Okay, start talking.
The Doctor: Wolfgang Amadeus Mozart had perfect pitch—Scorby: What happened to him?The Doctor: Who, Wolfgang Amadeus? (looks at the corpse next to him) ...Oh, him! Oh, he died of a pod.
- Little Old Lady Investigates: Amelia Ducat, quite awesomely so.
- Man-Eating Plant: As the Doctor notes in the first episode, on planets where the Krynoid gets established, the vegetation eats the animals.
- Minion with an F in Evil: Keeler is only a botanist, sure, but you'd think Chase would've sent someone more ruthless to assist Scorby in Antarctica. Keeler objects to everything Scorby does and even initially refuses to use a gun. When he finally accepts a gun the poor guy is such a nervous wreck it's amazing he doesn't accidentally shoot himself.
- Molotov Cocktail: Scorby makes one to fight the Krynoid. This scene earned the wrath of the Moral Guardians (see below).
- Moral Guardians: One of a number of Who stories from the era to be specifically attacked by Mary Whitehouse. In this case, she complained about "strangulation by obscene vegetable matter" and the possibility of children imitating the scene where Scorby makes a petrol bomb.
- Mysterious Antarctica
- Neck Snap: The Doctor notoriously appears to do this to Scorby at one point, although it was non-fatal because Scorby gets up with the only side-effect being he has a sore neck and is really pissed off. As opposed to actually breaking his neck it appears the Doctor just twisted it enough to momentarily stun him.
- The novelization by Phillip Hinchcliffe (who produced this story) has the Doctor knock out Scorby with a "Venusian Neck Lock".
- Not My Driver
- Not with the Safety on, You Won't: Scorby sabotages Stevenson's rifle by removing the firing pin.
- Obstructive Bureaucrat: The Doctor demonstrates how to get their co-operation."If that pod germinates it will mean the end of everything, EVERYTHING you understand? Even your pension!"
- O.O.C. Is Serious Business: You know it's a dicey prospect when Four not only starts screaming, but actually starts punching people.
- Open Heart Dentistry: When one of the staff of the Antarctic research station needs an alien-Virus-infected limb amputated, a zoologist is tasked to perform the emergency surgery because he's a better choice than the geologist or botanist: at least he's held a scalpel before, if only for dissections.
- Plant Aliens
- Plant Wrongs Activist: The first thing Chase says is how making bonsai is plant mutilation. He spends the rest of the serial not caring for human life at all.
- Put on a Bus: This serial marked the last appearance of UNIT in the series for a long time. Except for a minor appearance in The Five Doctors, there wouldn't be another UNIT story until Battlefield 13 years later.
- Pragmatic Villainy: When Amelia, who Chase tried to welsh on earlier, comes around demanding her money for the painting she did, Chase not only pays what he owes but doubles it in order to get her out of his house as quickly as possible. See also Rewarded as a Traitor Deserves below.
- Private Military Contractors: Scorby. Chase's house is also guarded by his private security force armed with Uzis.
- Real Life Writes the Plot: The whole studio recording schedule had to be heavily reworked when one of the principal guest actors came down with chicken pox.
- Recycled IN SPACE!: The Quatermass Experiment IN DORSET! — when it's not being The Thing from Another World or "The Man-Eater of Surrey Green".
- Redemption Equals Death: Dunbar.
- Rewarded as a Traitor Deserves: Completely averted. Chase actually pays Dunbar, his spy in the World Ecology Bureau, the briefcase full of money he promised him rather than killing him.
- Save the Villain: The Doctor tries to save Chase, who responds by trying to pull him into the compost machine with him. Big mistake, as it's difficult to hold onto someone while your legs are being crushed.
- Screw the Rules, I Have Money!
- Screw This, I'm Outta Here!: Most of Chase's guards wisely bail offscreen when things start getting rough, except for one who apparently wasn't fast enough and gets killed by some vines.
- Sealed Evil in a Can: The Krynoid pods.
- Self-Disposing Villain: See the Save The Villain example above.
- Sissy Villain: Chase: "I could play all day in my green cathedral!"
- Smug Snake: Chase is unbelievably punchable.
- Stuff Blowing Up: Yet another grand old British manor bites the dust in the last episode.
- And the Antarctic base at the end of Part 2.
- Stylistic Suck: Chase's music.
- Super Window Jump: The Doctor diving through the skylight to rescue Sarah.
- Suspiciously Similar Substitute: Two this time: Sergeant Henderson for Benton and Major Beresford for The Brigadier.
- Tap on the Head: Chase knocks Henderson out by bopping him lightly with a big wrench.
- Transflormation: Anyone infected by the Kyrnoid will be transformed into a murderous plant mosnter.
- Utopia Justifies the Means: The Krynoid seems to have this as an instinct. Chase likewise feels this way when it comes to plants.
- Viral Transformation: What the Krynoid does to its human host.
- Was Once a Man: Winlett, then Keeler.
- When Trees Attack
- Whole Plot Reference: To The Thing from Another World.
- Wrench Whack
- The X of Y