The post-apocalyptic book The Day of the Triffids features not one but (at least) three seemingly separate disasters:

  • triffids themselves, obviously
  • blinding lights in the sky
  • plague

I somehow hoped that the exact cause of the disasters and if they were related to each other anyhow would be revealed in the book. It wasn't unfortunately. Although I must admit that it made the story much more realistic, since the survivors would hardly have access to any information easily in a broken world, I was a little disappointed.

There were several occurrences in the book that hinted a possible connection between them:

  • triffids started attacking the people almost immediately after the lights blinded them, as if they interpreted that as an order to attack.
  • the plague was strangely killing the blind more easily than the seeing ones, as if it was another effect of the exposure.
  • the main character assumed that the lights were a part of an orbital weapon accidentally activated by the meteor shower. He also suspects the plague not to be a natural one, implying that it was also spread by an orbital weapon.

I assume that these questions were deliberately left open, however I wonder if John Wyndham ever explained them in an interview or elsewhere? I limit my question only to the book, not any of the screen interpretations.

3 Answers 3


The story is partially an allegory about unchecked scientific advances particularly in the mysterious military/industrial complex that was so powerful in the world (both western and in the USSR) following World War II.

The triffids themselves were a product of advanced breeding techniques (today we might say genetic engineering, but those techniques were not available at the time) with the objective of providing cheap fuel oil at the expense of introducing a very dangerous plant into the environment. The plants themselves are released in an accidental manner.

As you say, the main protagonist Bill Mason wonders whether there was really a meteor shower at all and whether the blinding lights and the plague were a result of a weapon gone wrong, but nothing is specifically confirmed in the novel.

I think it is clear that the events are not an orchestrated attack, and more of a result of the blinding of most of the population of the planet. The triffids are intelligent and become aware that they are not being tended and break out of their farms and attack humans because they are naturally aggressive and lots of blind humans and animals give them plenty of food. The plague appears to be connected to the blindness, but that might simply be a result of the victims not being able to avoid affected people or contaminated food and water.

I know of no specific interview where Wyndham confirms these suppositions, however many of his novels are about similar themes of the impact of new technology on mankind, eg. The Chrysalids about nuclear war, and Trouble With Lichen about an anti-aging drug (and his best novel in my opinion)

The story doesn't give anything away other than the theories of the main protagonist Bill Mason. The "moral" of the story is that if you set these dangerous conditions up, the chances are that something bad will happen, with enormous consequences. Its not really to Wyndham's benefit that these are revealed in detail allowing the reader to pick at the plausibility of the situation.

  • Great mention that the "meteorite shower" might have been a weapon. But Triffids intelligent? I thought they were acting on instinct. Apr 14, 2012 at 20:50
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    @Wikis. Bill Mason starts out thinking that it is just instinct, but the experiences he has when he is living in the house with Susan's friends and trying to keep triffids out of the property, he starts to believe that they are intelligent (at least to a point - after all I am saying 'intelligent for a plant') Apr 14, 2012 at 20:56
  • Thanks, good response. Of course, "intelligent for a plant" is any IQ above zero... :) Apr 14, 2012 at 21:06
  • One of the characters commented that triffids seemed to have some kind of swarm intelligence: groups seem to act in a coordinated manner. May 30, 2018 at 7:44

I know of no explanation by Wyndham, but my impression was that the other disasters were entirely "mundane" within the context of that world, in that they were natural consequences of almost the entire population becoming blind.

The triffids were always aggressive towards humans. The mass blindness allowed for their escape from captivity and rampant breeding.

As to the plague, when society breaks down, diseases that could previously be easily controlled could easily become highly deadly without the infrastructure to treat them. (Cholera, for example, is rare and almost invariably survivable in first world countries but a major source of death in the less developed world.) It could simply be that the blind are more susceptible because it is harder for them to identify and stay away from those who are infected.

No clear explanation for the blinding lights is ever offered in the book. As a major theme of book is the illusion of control and fragility of technological society, I suspect Wyndham may have intended them to be inexplicable.

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    "I suspect Wyndham may have intended them to be inexplicable" - possibly although JW rarely went into detail concerning the technology in his stories (unlike Tom Clancy on cyber applications, Arthur Clarke on space propulsion or Verne exploring biological aspects). He was focused on the story / allegory / message rather than the tech and its a significant influence on those who came after like Stephen King. Wyndham took Wells approach of combining 'reality' with 'science' in a 'what if' situation. The situation, characters and how they react are the point, rather than the technology itself. Oct 4, 2016 at 10:27

IIRC, Bill recalls one of his former colleagues telling the tale of the origins of the Triffids. It was his pet theory that the aircraft smuggling a sample of triffid seeds out from behind the iron curtain was shot down and broke up in mid-air. This allowed the spread of the seeds, on the high-altitude winds, all around the globe. All of this was several decades prior to the blindness.

As to the cause of the blindness/plague, I thought that this was explained as a collision between two orbital weapons, one carrying the plague, and the other the blindness-causing material. Although this was put forward as conjecture by Bill.

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    Welcome to SFF! This seems like it could be a decent answer to the question but could you edit in the source/evidence for all this? Also don't forget to register your account and take the tour!
    – TheLethalCarrot
    May 29, 2018 at 11:44
  • Yes, the book does mention a plane being shot down as the release of the triffids into the wild. I don't recall the collision theory. Bill does theorize that the blindness was a space based weapon and that its terribly coincidental that the plague arises at the same time - but there's no definitive cause ever given. May 29, 2018 at 18:53

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