It's around the mid-2300s. Earth is, to put it simply, in trouble. Climate change has resulted in flooding of major coastal cities, displacing billions, which ultimately led to widespread conflict and death. Resources are dwindling, which leads to further conflict between major world powers.

There are colonies off-world. Habitats on the Moon, and cities on Mars, which is in the process of being slowly terraformed. There are populations on Ganymede, Titan and Europa, and orbital cities around Jupiter.

In the midst of all this, from the depths of interstellar space, a small craft of some kind comes hurtling. It's cloaked to satellite detection and it travels for years until it finally lands on Earth. The craft contains a strange extraterrestrial life-form - basically just a small, black mass, pretty much a gross-looking goop.

It lands in, let's say, a small forest somewhere in China. A forager wandering around finds the craft and checks it out of curiosity. Unfortunately for him, the black goop senses life and essentially takes over the man, making its way through his oral cavities and into his brain. This is Patient Zero - but he doesn't die.

In a strange quirk of handwavium biology, the life-form, after burrowing itself into the man's head, produces a highly contagious airborne virus-type thing. Once the virus gets into another person's body, it's supposed to grow into another organism like the initial life-form.

But that's not what happens, at least, not to everyone. The vast majority of people contract the "virus", but it doesn't grow into anything. It incubates within their body, and given that now population density is even greater due to displacement, and air travel is a given, soon, the vast majority of the world is infected.

After a few months, the deaths start, almost all at once. Hundreds, then thousands, and then millions. It's too fast for world militaries to do anything about it. The deaths cause widespread panic, unrest and riots. Martial law is enacted but again, too little too late.

As the death toll gets into the billions, two other things emerge: some people are immune to the virus, as in it doesn't get into their bodies and affect them at all. Furthermore, there are some people for whom the virus did work, and actually grew into the parasitic life form in their heads.

The world lies in ruins, and as the survivors try to make sense of what happened and rebuild, this new threat emerges. The "infected" can "manually" force the parasites into the immune, and grow their numbers that way. The parasite is an intelligent creature; it's actually fleeing its own ravaged homeworld (there's more backstory on that), and its only goal right now is to infect as many as possible and create an army of host bodies.

The colony worlds have no idea what to do. They're too busy trying to survive on their own worlds and create something stable in extreme and hostile environments. They don't have the means to come to Earth and help - Earth is on its own.

Does this make sense? I know it's far from hard science or realistic but just based on its own merits, does it seem plausible? Any holes I may be missing?

  • $\begingroup$ Well written, maintained suspense well, reversals, very readable. Not an ideal question on this site however. I've added the reality-check tag, because that seems to be what you are asking here, please edit to revert that if you feel appropriate. $\endgroup$ Sep 18, 2019 at 2:04
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    $\begingroup$ Whether or not it is plausible will probably depend on whether or not you make it so. As the creator, you have the power to say whether or not it is. $\endgroup$
    – Andrew Fan
    Sep 18, 2019 at 2:05
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    $\begingroup$ Alien gross-looking goop has been done many times in horror and suspense movies, so most folks know to make a phone call to the emergency services when they happen upon a crashed alien spacecraft in the woods. $\endgroup$
    – user535733
    Sep 18, 2019 at 2:22
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    $\begingroup$ There seems a big assumption here that the intelligent alien parasite will be able to draw upon the knowledge of the host (like The Puppet Masters, 1951). The parasite can't accomplish much if it can't talk human or read signs or drive cars or make phone calls. However, recorded cases of real, Earthly behavior-altering-parasites can't draw on host knowledge nor skills nor generally exercise fine motor control - the host brain seems NOT an impotent and pliable puppet. $\endgroup$
    – user535733
    Sep 18, 2019 at 2:29
  • $\begingroup$ @user535733 from recent research on Ophiocordyceps unilateralis, it appears that it is possible for a fungus to exert motor control and drive around an ant's body without infiltrating the brain. Ant bodies are simpler than human bodies though, and the fungus has had quite a long time to adapt to them... $\endgroup$ Sep 18, 2019 at 12:25

2 Answers 2


Plausible? No. Works for a story? Sure.

That's not to say it couldn't form a good premise for a soft sci-fi short, or something of that nature, or perhaps a background for a dystopian setting. But there are just two many problems to deal with here for this to be plausible.

DNA. This gets addressed a lot in xenobiology questions, but there's no reason to assume that an alien species has the same DNA structure as humans, let alone uses DNA to store information. It could use something else entirely to encode information. And that means that if it comes into contact with a human, the whole 'virus' thing isn't going to cut it - it'd be like trying to pick an electronic keypad lock with a skeleton key. And then there's another problem.

Biochemistry. Even worse than a DNA mis-matchup, to replicate itself off humans it needs to use organic molecules - and there's nothing which guarantees that it uses the norms found on Earth. If it's silicon based rather than carbon, no dice. If it favors L-proteins, no dice. If it requires vitamins that it can't synthesize on its own which we don't have - no dice.

Brain parasites. We don't really understand how brains function. But even still we have a problem - memory. You specified 'virus', which is a single cell organism (maybe - it's not really a cell at all) and has a very small amount of genetic coding within it. Fact is, even if it somehow could overwrite a human's ability to control their brain, I don't see how it could carry a set of instruction beyond basic instinct, and it would need to use a human brain, which it does not understand, for any higher level of thinking. And it would need to be smart. Because the immune humans have guns and don't want to be infected.

Virus to parasite. These are two very different things. Now this sounds more like a mold, seeing as it can function at the cellular level and the visible level (this parasite sounds like a large complex organism). It's kind of hard to justify a virus somehow being able to grow into a mold.

Mass Death. This isn't a problem with the mechanism, it's just that why would a brain parasite kill a massive amount of its hosts at once? This seems like a very unique and specialized organism, so why would it trigger host death? That's more of less a dead end. Even immunity is better than host death from the virus's perspective, because apparently it can be forced into other people from the infected.

Space travel. It travels as an organism? I mean, sure, theoretically possible, but once again, this isn't really a virus if it comes from an organic shuttle capable of interstellar transport and atmospheric re-entry. This sounds more like a very complex organism which is made of a lot of unique and separate life-forms, like a virus for marking humans, spores which build off the markers, and a 'base' for this whole thing which is the crashed organic spaceship which houses some form of mother brain which controls the whole thing.

But, as I pointed out at the beginning, it's fine from a soft sci-fi standpoint, as long as you (the writer) know that at the beginning and don't try some terrible explanation to justify it to your readers.

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    $\begingroup$ Plausible? No. Works for a story? Sure. +1 $\endgroup$ Sep 18, 2019 at 6:00
  • $\begingroup$ If it is some sort of a mold and can communicate to other mold colonies (infected people), it could be trying various ways of synthesizing what it needs to survive and failing, resulting in the host's death. Each attempt is a different distinct "cause of death" stemming from the same cause, but at the surface doesn't look connected. $\endgroup$
    – JRodge01
    Oct 21, 2019 at 18:03

Deaths all at once is tricky.

You need the virus to turn deadly everywhere, all at once. Otherwise there will be quarantines, research and all that. Similar to this question: How could a seemingly-harmless virus become deadly at a predetermined date and time?

Even with rapid and unnoticed spread, there will be many months between initial and final infections. How does the infection time it so that bad stuff happens all at once? It is an intelligent life form, but unless it is psychic there is no way for the individual infections to coordinate the second stage. I suppose if every infection is actually the same alien with the same memories and so on it could watch for some event that would be noticed all over the world (moon next to Venus?) and start the second stage then. But it sounds like the whole world infection thing is not going as intended for the alien.

Aliens controlling humans and infecting other humans is good standard Puppetmasters SF stuff. I liked the idea of the alien reproduction scheme going haywire and if the original goo alien is a refugee itself, maybe it is horrified at what it has done.


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