The book's narrator is an Englishman named Bill Masen, who details how some years previously the eponymous carnivorous plants mysteriously began to appear all over the world, eventually proving to be capable of movement and possessing the ability to attack humans with their poisonous stings; Masen's own theory is that they were deliberately bioengineered in the Soviet Union and then accidentally released into the wild, but the truth is never revealed. Whatever their origin, the plants are also discovered to produce a high-quality vegetable oil, and so an entire industry grows up around farming them. Masen works as a researcher on a Triffid farm, and ends up in the hospital after a Triffid stings him on the face. His eyes thus bandaged, he misses a bizarre meteor shower that lights up the night skies all over the world.
Come morning, Masen learns that the shower has struck blind everyone who viewed it. (He later speculates that the shower was actually a malfunctioning orbital weapons system, but again no proof is to be found one way or the other.) Wandering through a disintegrating London, he meets and quickly falls in love with a sighted novelist named Josella Playton (who missed seeing the "meteor shower" because she was sleeping off an unfortunate party experience.)
While the Triffids rapidly break free of their farms and begin wiping out the blinded population, Masen and Playton become entangled in the squabbles of other sighted survivors leading to their unwilling separation. They are finally reunited at a small estate in the English countryside, taking up farming in a fenced enclave surrounded by hordes of Triffids. When a despotic new government appears on the scene, they join a colony of more freedom-minded individuals on the Isle of Wight, researching for the day they can defeat the Triffids and reclaim the Earth for humanity.
In 2001, the author Simon Clark wrote a sequel to the book entitled Night of the Triffids, which attempted to be a pastiche of Wyndham's style, and details the adventures of Bill and Josella's son.
The novel has been adapted for film three times, first by a very loosely-adapted 1962 feature film; then by a 1981 BBC miniseries which, while low-budget, is quite faithful to the original work; and once more by the BBC in 2009, again with the plot deviating a great deal from the original.
- America Saves the Day: Coldly deconstructed in the original, where Apathetic Citizens who assume that aid will come from the United States as it did in WW2 end up triffid fodder.
- Apocalypse How: Killer plants and blinding "meteors". Performs a relatively mild Class 1.
- Attack of the Killer Whatever: Killer plants, in this case.
- Baby Factory: One of the most horrifying aspects of the plot's entire setup is that they cannot possibly help the vast majority of the population, who have been blinded. Eventually even the "Good" faction of people led by Beadley sadly concludes that all of the blinded men are a drain on resources and thus a complete write-off. Conversely, Beadley's openly stated position - grudgingly accepted even by the protagonist - is that blind women of childbearing age will be kept alive and in polygamous relationships with the remaining sighted men, to try to repopulate as quickly as possible.
- Both Sides Have a Point: Bill Masen is initially somewhat shocked at the pragmatic abandonment of most of the blind population in London by Beadley and the Institute group, and sympathizes with Coker's more idealistic attempt to help them. Ultimately, he comes around to the Beadley position when Reality Ensues, as does Coker himself.
- Chekhov's Gunman: The Evil Redhead who shoots at Bill's blind group later appears as a member of a new despotic government.
- Cosy Catastrophe: As noted, perhaps the most famous example. Which is not to say it doesn't have its not-at-all cozy moments...
- Depopulation Bomb
- Evil Redhead: Torrence is first seen casually firing on Bill's blind group so they won't compete for resources. When we next see him he's posing as a member of a restored government (actually a feudal military dictatorship).
- Fate Worse than Death: Obviously, everyone who's been blinded. Even though Josella's heartbroken at her father being killed by a Triffid, she believes he would have preffered it to being blind - "He loved all this too much."
- Gone Horribly Wrong
- The Triffids are implied to have been genetically engineered, and made to survive in very inhospitable environments.
- It's also implied that the 'meteorite storm' was in fact a satellite weapon that collided with something, and not only caused blindness but might have had something to do with the sudden outbreaks of viruses and diseases.
- The Great Politics Mess-Up: Averted in the book, kind of; Wyndham liked to throw in a bit of exposition about the Soviet Union for the benefit of future generations too young to recall the Cold War. Illustrated neatly by a scene in the first chapter when a shady individual claiming he can supply triffid seeds to a British firm points out that dealing with the suppliers directly might be difficult; in the book, this is the cue to pause the action for about half a page of exposition. In the 1981 TV adaptation, the company executive sums it up with one sentence:"You mean they are behind the Iron Curtain."
- In Medias Res
- Irony: Sight being the greatest advantage humans have over triffids, the plants usually attempt to blind their prey with their stings. A triffid sting is what lands a temporarily blinded Bill in hospital, ultimately saving his eyesight and his life.
- It Can Think: The exact level of intelligence of the genetically-engineered triffids is a subject for debate, with the protagonist rubbishing the idea that they're intelligent after all, dissections haven't found anything remotely like a brain. Others aren't so sure. One man points out that the triffids escaped from their farms within hours of everyone going blind. In another scene a triffid is waiting outside the very door which a person would run out of if they heard someone driving down the road. Much like the Velociraptors in Jurassic Park, they're also smart enough to avoid an electrified fence...and to force it down when the electrical power is off. They even have a crude form of communication by drumming their branches against their trunk, though whether this is a crude but effective "hunting call", or an actual complex "language" is unknown. Overall, they seem to have at least the same basic intelligence level as a pack of dogs.
- Just Think of the Potential: Used both positively and negatively; the money to be made from the Triffids' oil, while pre-disaster one of Masen's colleagues speculates about Triffids' advantages over a blinded human.
- Kill It with Fire / Fire-Breathing Weapon: Flamethrowers prove to be the most effective anti-Triffid weapon, although a lack of fuel is a major problem.
- The Last Man Heard a Knock...
- Mainlining the Monster: Triffids are initially culled because their predatory habits pose a threat to humans, but when it turns out they can be exploited as a source of a high quality oil, they are captured, have their stingers removed, and farmed instead. Even worse, when it turns out that the oil quality improves if the sting is not removed...
- Man-Eating Plant: At least, after we've... ripened... a bit.
- Missing the Good Stuff: Masen initially feels this way about being blindfolded during the spectacular meteor shower. Soon enough, of course, he comes to realize what a truly lucky break it actually was.
- Never Live It Down: Invoked by Josella and her "scandalous" novel Sex Is My Adventure. The 1981 adaptation, being made in much less straitlaced times, quite sensibly dropped this aspect.
- No FEMA Response: A plot point. The first third of the book and the original TV adaptation is driven by the conflict between one faction of sighted survivors who are desperately trying to hold things together until an official relief effort of some sort arrives, and another group who have concluded that there isn't going to be one and they should salvage what they can and get out while the going is good. The second group turns out to be right, and the desperate attempts to keep hundreds of blinded and near-helpless people alive were all for nothing. Being a Cosy Catastrophe doesn't stop this book being pretty bleak in places.
- Reality Ensues: One of the greatest and earliest examples of this trope in apocalyptic literature. The author takes the general "survive the Zombie Apocalypse" horror story (using plants instead of zombies or nuclear war), and extends it forward for several years. Quite simply...scavenging for canned food in the ruins of major cities is not a viable survival strategy on an extended time scale. Crowds of blind people scavenge in the early days, but there's a finite supply of canned food and they run out eventually. Nor do the more lucky survivors simply flee to a pastoral existence raising their own crops in the countryside. The author repeatedly underlines the point that even those who survived long enough to plow their own fields, need to learn how to forge their own iron to make their own plows. If they're just scavenging old plows, they're not much better than the blind people scrabbling for cans in ruined shops. The entire set of interconnected relationships that are required for civilization are needed for long-term survival.
- Riddle for the Ages: So where did the scary plants and populace-blinding meteors come from? We'll never know.
- Slept Through the Apocalypse: As noted, both Masen and Josella were out of commission during the meteor shower that blinded everyone.
- Soviet Superscience: Masen speculates this might have been the origin of the triffids. While he is more knowledgeable on the subject than the average man on the street, he is still basing this on second and third-hand rumors he picked up during his work with the triffids.
- Suspiciously Specific Denial: The U.S. specifically states that it has no satellite weapons that will directly wage biological warfare on human beings. Other countries with the ability to actually place satellite weapons refuse to even do that, because everyone can see that the U.S. is using an Exact Words denial.
- Synthetic Plague: Speculated to be the cause of the disease that wipes out many of the survivors of the initial disaster. The symptoms are similar to typhoid fever, but unusually fast and apparently with a near perfect fatality rate.
- When Trees Attack: And how.
- Zombie Apocalypse: Triffids aren't undead humanoids, but in terms of behavior and threat level they share more than a passing resemblance.
- Zombie Gait
- The blind, who are shuffling around mindlessly pawing at things and wailing — they were sighted a few hours ago and with no experience in living without it or anyone to help, they're stumbling around in the dark. Subverted towards the end of the book by the original inhabitants of the farmhouse, particularly Dennis, who is determined not to let his blindness imprison him.
- Again, the Triffids themselves lurch slowly about using their three "legs".
Examples specific to Simon Clark's sequel:
- Acquired Poison Immunity: The revelation of how humanity can take Earth back from the triffids. Small doses of triffid venom, combined with eating triffids, can help immunize people from the venom.
- America Saves the Day: The sequel completely subverts this. Partially Double Subverted when the Native Americans that live near a La Résistance base help David to discover the solution to how to take the planet back from the triffids.
- Baby Factory: A non-enforced version appears in the Isle of Wight, where blind and sighted women live in great houses together, having children with any man they choose, and taking care of the children communally. The New York community has women basically treated as slaves, forced to have many multiple pregnancies.
- Big Applesauce: Seems to be an utopian community, protected from triffids thanks to blocked bridges. The utopia part is a lie: there is a segregation system between white sighted people and the rest and slavery runs rampant in northern Manhattan (where factories manned by blind people, those who made the mistake of complaining about the system and those who are too weak run 24/7) and some other places (where the workers are forced to work non-stop to cut trees for ethanol or to mine coal) and many women are forced to become a Baby Factory. Being the child of New York's leader won't save you, and in fact he will send you to that destiny because of his relation to you.
- Call-Back: The beginning is a call back to the beginning of the original novel: both characters wake up unable to see anything, and think that when the situation is similar to what is going on then, something very bad is happening.
- Chekhov's Gunman: General Fielding, the leader of the New York community in the sequel, is mentioned about still having some red hair amongst the white hair, and a blind eye from being hit there by a triffid. He is actually Torrence, the Big Bad of the first book, who managed to survive the triffids' attack at the end of the first book.
- Foreshadowing: David finding Christine alive in the floating triffid island despite the fact that she has probably been living with triffids for most of her life. It is the signal that people can become immune to the venom.
- Kill It with Fire: There is a special anti-triffid squad armed with flamethrowers, always ready to go at the first signal of one or more triffids making their way to the Isle of Wight, or when there is an expedition to Britain.
- Bill Masen comments with David about the irony of triffids being both their greatest enemy and their greatest source of fuel.
- Since all the fuel the Isle of Wight uses comes from triffids, it means that the anti-triffid squads' flamethrowers must be fed with triffid oil. So, they are killing triffids with the remains of their fellow triffids.
- Torrence, who hates blind people and the Masen for their role in leaving him half-blind, is finally toppled thanks to a march by blind people whose children are soldiers, and ends up being blinded by David Masen.
- La Résistance: A group with bases somewhere in the East Coast and in the Great Lakes is opposed to the semi-fascistic New York regime.
- Medieval Stasis: Bill Masen tells David that the Isle of Wight community has hardly changed in the thirty years since it was established, and that, apart from a few things, the only thing they are able to do is to restore old things. He predicts their community will die if something is not done soon.
- Nothing Is Scarier: At the start of the novel, it is completely dark, and David only has a lamp without mirrors to see the path. He can't see the triffids that he knows are coming, which adds to his nerves.
- Sequel Hook: at the end of the novel, a transmission is detected from somewhere else in the world, and an expedition is announced to find those people.
- The Night That Never Ends: The novel begins at 9 AM in summer, and when the main character awakens it is as dark as midnight in winter. A combination of very dense clouds and an asteroid cloud passing between the Sun and Earth is the cause. Later in the story, when the clouds leave, there is light, but the sun looks like it is dying.
- Universal Poison: The triffid venom is shown not to be this. A lecture in the first chapter tells that it is not an instant killer, but the antidote has to be injected into the carotid artery very soon.
- Utopia Justifies the Means: General Fielding (also known as Torrence) thinks this.
- Wild Child: Christine manages to survive surrounded by triffids for more than ten years, after her father died of cancer when she was four.
Examples specific to the 1962 film version:
- Adaptation Expansion: Brutally shows the horror of those first few days in two scenes; one shows an ocean liner, helplessly adrift, and the second an aeroplane pilot begging for someone to talk him down, as the entire crew is blind. The plane crashes near Mason's ship, but we never find out what happened to the liner. It also adds a subplot of American marine biologist Tom Goodwin and his wife Karen (played by Janette Scott), who are trapped in a lighthouse because the relief ship didn't came as a result of the blindness and are eventually besieged by Triffids.
- America Saves the Day: Embraced in the movie version, wherein Goodwin eventually fights off the triffids with the lighthouse's firehose out of sheer Last Stand desperation and thus discovers their the Weaksauce Weakness—sea water.
- Chekhov's Gun: The "SEA WATER — EXTREMELY CORROSIVE — FOR FIRES ONLY" water hose that is used by Goodwin to kill the Triffids in the final act is shown very deliberately in an early scene
- Death of a Child: Kept mostly to off-screen insinuation, but the scene with the airliner that crashes because of the pilot being blind and the passengers rioting when they figure it out prominently has a kid amongst said passengers (the air hostess tries to reassure the kid but the passenger right next to him instantly catches up that it means the pilot is blind, starting the riot, and the kid is tossed aside as they all scramble to the front of the plane).
- Evil-Detecting Dog: One of these starts barking at a triffid, only to be killed by it offscreen.
- Kill It with Water: Bizarrely used as the monster-killer in the first movie adaptation.
- Moral Dissonance: Mason returns to the chateau to find sighted convicts holding the blind women at gunpoint and sexually assaulting them. He gets Christine Durrant and Susan into the truck and drives away, making no attempt to save the helpless women. Even Durrant - who earlier had vowed not to abandon the others - never mentions the chateau incident again.
- Plant Aliens: As noted, the original didn't establish where they came from (casually speculating on aliens and Soviet Super Science); the movie version explicitly made them into aliens.
- Promoted to Love Interest: After Josella was removed from the 1962 movie version for God knows what reason, they decided to replace her role in the story with Durrant of all people!
- Revised Ending: See Kill It with Water above. It essentially gives the plot a "God will provide" ending similar to George Pal's The War of the Worlds.
- Screaming Woman: Janette Scott in the movie. And despite that famous line from "Science Fiction / Double Feature" in The Rocky Horror Picture Show, she doesn't actually do any fighting.
- Touch of the Monster: The movie version's advertising poster.
- Weaksauce Weakness: Again, the water thing (in the movie). Or maybe seawater; the narrative isn't very clear on this point, possibly because the whole subplot was allegedly added on rather late in production as quite literal filler because they needed additional run-time for a theatrical release. Try not to think about it too hard.
Examples specific to the 1981 Television Series:
- Adaptation Distillation: The slightly patronising depiction of Coker is done away with, as is the whole Sex Is My Adventure sub-plot with Josella.
- Adaptation-Induced Plot Hole: Those orbiting KillSats that are mentioned so prominently in the original book never really came to pass, yet in the last episode Bill attributes the blindness plague and whatever mysterious sickness wiped out the survivors in London to some of them going off accidentally. Although it's downplayed significantly by the fact he's only speculating.
- Apocalyptic Logistics: Lampshaded by Coker.
- British Brevity
- Compressed Adaptation: Characters and sub-plots are ruthlessly pruned to fit the whole story into six hours. Arguably an improvement, as the novel had a tendency to meander a bit.
- Large Ham: John Duttine as Bill Masen, in noticeable contrast to every other version.
- Setting Update: It's not clear when the original novel is supposed to take place, but it was clearly Next Sunday A.D. from the perspective of The '50s. The producers took the decision to set it very definitely in The '80s instead, which was probably for the best.
- Trailers Always Lie: The anti-triffid guns showed up in a lot of publicity stills, but only ended up being fired once on-screen. This was probably because the firing effect had to be done with CGI, which looked extremely unconvincing.