Harrison Chase: "What do you do for an encore, Doctor?"
"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 Krynoid, speaking through Harrison Chase
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
- Art Shift: Third of four Tom Baker stories 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.
- 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.
- Berserk Button & Beware the Nice Ones: This is one of at least two times during Four's tenure where the normally goofy Doctor is PISSED. THE FUCK. OFF.
- Body Horror: There's no other way to describe the Krynoid transformation.
- Bond Villain Stupidity: Scorby, all the time.
- 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.
- 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.
- 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 Krynoids 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.
- 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.
- 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.
- 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.
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.
- 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 an anonymous security guard at one point, although it appears to have been non-fatal.
- Not My Driver
- Obstructive Bureaucrat: The Doctor demonstrates how to get their co-operation.
"If that Krynoid spawns it will mean the end of everything, even your pension!"
- Open Heart Dentistry: When one of the staff of the Antarctic research station needs an alien-Virus-infected limb amputated, a biologist is tasked to perform the emergency surgery because he's a better choice than the geologist or botanist: at least he's probably held a scalpel before, if only for dissections.
- Plant Aliens
- 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.
- Recycled IN SPACE!: The Quatermass Experiment IN DORSET! — when it's not being The Thing (1982) or "The Man-Eater of Surrey Green".
- Recycled Script: Noticeably recycled from an episode of The Avengers (not by the same writer). Also strong similarities to The Quatermass Experiment.
- 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.
- 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.
- Utopia Justifies the Means: The Krynoid seems to have this as an instinct. Chase likewise feels this way when it comes to plants.
- Was Once a Man: Winlett, then Keeler.
- When Trees Attack
- The X of Y