I have this shapeshifting alien living on earth posing as human. He does not follow any "alien agenda", just trying to blend in to ensure his survival. He has a wife, children, stable job etc. Never does anything unhuman-like. Now he is about to be exposed.

How could humans (preferably his own wife) possibly find out about him?

Important thing is, he knows this is about to happen before it actually happens, but he is powerless - or maybe not motivated enough - to do anything about it. Could be some mistake he made that is too late to fix.

Here is some more information that might help:

  • This guy is way older than Earth itself, he has been living here since before humanity, posing as different people/animals, faking aging and death every time.
  • He can simulate human organism (or any organic/inorganic matter) down to molecular level. It takes less than a second for him to change form and he does not do it often, only when he is about to assume a new identity for another 60 years or so. Last time he did it was decades ago
  • His kids are completely human, anything alien that was ever in them was a single simulated sperm cell.
  • He is the only one of his kind, nothing like him ever existed.
  • He is of above average, but still humanly intelligent. Very experienced with pretty much everything because of his age.
  • He is totally capable of being killed (albeit harder than regular humans), only thing that ensured his long age before and on Earth are his unmatched survival skills. (Not sure if this is relevant to the question)
  • There are about 5 to 10 other immortal beings on Earth (superpowered humans, not aliens) that knew about him, but forgot a long time ago. Besides them, everybody that ever knew about him (human or alien) is long dead.
  • This takes place on present-day Earth. No alien-detecting technology has been developed and wil not be for some time.
  • He does get exposed from time to time (once in about 1000 years on average). When this happens, he fakes his death and changes identity again.
  • He did live on other planets before Earth, left only when given civilization went extinct or drove him away
  • $\begingroup$ This is similar to "Man from earth." In that movie they couldn't expose him until he explained it himself. $\endgroup$ Jun 5, 2017 at 11:09
  • $\begingroup$ Could it happens occasionly or only option is the 'he predicted they will know about him'? $\endgroup$
    – ADS
    Jun 5, 2017 at 11:11
  • $\begingroup$ I don´t quite understand what do you mean. He has to know in advance (days or just minutes, doesn´t matter) he is about to be exposed. NO, he can not predict the future, and YES it does happen every few thousand years. Gonna edit my question... $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 11:21
  • $\begingroup$ How did he travel between planets? $\endgroup$
    – ozone
    Jun 5, 2017 at 12:43
  • $\begingroup$ On a space ship, obviously. Or maybe he can shapeshift into a spaceship himself. $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 12:49

3 Answers 3


You could put him in a life or death situation where he and his wife and children are trapped and the ONLY way to survive would be to shape-shift into something that could handle the situation.


  • Forest fire and cut off from rescue: The only way out is by air, he knows that the only way to get his family out is to shape-shift into a gigantic bird and fly out with his family on his back, or something like that.
  • Trapped in rising flood waters: He needs to shape shift into either a boat or an animal that can get them all out.
  • Home invasion: Well armed intruders are going to kill his family if he doesn't do something.

Take a situation like any of the above where his options for anything else are slowly being taken away, one by one, so that his ONLY remaining option is to shape-shift of lose his family. This approach will allow you to build dramatic tension.

Take the fire for example. They know it's closing in, so first, they try to drive out, but the roads are blocked, then they try to radio for help, but high winds make an air rescue impossible. Things get more and more desperate as he looks for any other way to keep from revealing his secret, until finally, there is no other way.

Make him very fearful of doing so. Perhaps a back story of another wife in the past who was so repulsed by knowing she had been with a monster that she ran off, or killed herself, or, worse killed their children out of fear of them being monsters too. Make the stakes VERY high for him.

  • $\begingroup$ That sounds like an awesome story. But, he is not human, he just pretending. He does not feel love and would probably let them all die, their lifespan is nothing compared to his anyway. Maybe if he was trying to save someone, who is somehow important on a cosmic scale... $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 13:46
  • 1
    $\begingroup$ @J.Joscak Why not let that person be his wife or children? Also, maybe he just thinks he can't feel love, but having been around humans long enough has sparked at least a touch of empathy in him? $\endgroup$
    – user20762
    Jun 5, 2017 at 14:05
  • $\begingroup$ I do not want to get this too emotional or psychological, it would not go well with the rest of the story. And "how can a human woman be cosmically important" could be a whole new question... $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 14:24
  • $\begingroup$ @J.Joscak not all questions need to be answered. Michael Moorecock waited decades to reveal what Stormbringer was. Maybe he simply knows that she is important, but not why? $\endgroup$
    – user20762
    Jun 5, 2017 at 14:28
  • $\begingroup$ So basically he has to expose himself in order to save someone/something of utmost importance. I think I can work with that. Thanks $\endgroup$
    – J. Joscak
    Jun 6, 2017 at 6:51

Blood samples

He was recently involved in a health incident of some sort. Possibly an accident, or a sudden bout of illness, or similar. During this time, when he was unconscious/delirious, well meaning health workers took blood samples for testing. These blood samples will remain human for a while outside his body - a couple of days, a week, perhaps - but soon will revert to his natural state. At that point, the jig is definitely Up.


Similar to above, but instead of blood samples, he has contracted some kind of illness - even something simple, like chicken pox - which is interfering with his ability to maintain his shape. He knows that this is happening, but there's nothing he can do to wipe out he virus. In x-time, his shapeshifting ability will be temporarily suppressed, but definitely long enough for his wife to find out the Truth.


For a nastier version, perhaps someone is threatening his wife and children if he doesn't "Tell the truth". The blackmailer doesn't even need to know what the truth is - they could be talking about his business dealings, or have tracked an earlier identity and realised he's not who he says he is. But if he doesn't "tell the truth", the blackmailer will harm his children, or expose his secret.

  • $\begingroup$ That second one is really good because it also covers the issue of him knowing that his wife will soon know. $\endgroup$
    – ozone
    Jun 5, 2017 at 12:46
  • $\begingroup$ I like that idea with blood samples. But this can not be the first time he lost his blood as his current identity, can it? What about all the other blood he lost before (cut himself cooking, a bar fight...)? Did no one see it behaving weirdly? Then again, people usually do not keep spilled blood around for too long... $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 13:13
  • $\begingroup$ @J.Joscak Exactly, as long as he was careful to clean up spilled blood fairly quickly it wouldn't matter that much. Having a large sample being kept in sterile conditions and analysed by professionals is quite different from a random person finding an odd stain on their clothes after a barfight. $\endgroup$
    – Werrf
    Jun 5, 2017 at 13:38
  • $\begingroup$ @Werrf I like the idea of blood samples, with the caveat that it's starting to become a cliché`. It's been used in "The Thing" and in Star Trek Deep Space 9. Tropes are not bad, but it would be interesting to subvert the trope in this instance. good answer though +1 $\endgroup$
    – user20762
    Jun 5, 2017 at 13:58

I say there HAS to be something different about him. Otherwise, the instant he turned into a human so fully and completely that he could have a completely human son, he would essentially BE human, not alien. He could never change again.

You need to create some subtle difference--perhaps the blood mentioned above, that distinguishes him from a human.

Also, I find it a bit unrealistic that he could live millions of years without dying somewhere along the way. I would think you would need some kind of resurrection system. That's just my humble opinion.

  • $\begingroup$ That is kind of his who he is, an interstellar survival expert. He simply managed to survive against all odds. $\endgroup$
    – J. Joscak
    Jun 5, 2017 at 13:00
  • $\begingroup$ Ok, so when you said, "He is totally capable of being killed (albeit harder than regular humans)" I guess you meant harder on a scale of one to one million and one would be how hard it would be to kill a human and this guy is at the other end of the scale. Anyway, you got some good answers here. Are any of them satisfactory? $\endgroup$
    – ozone
    Jun 5, 2017 at 21:21

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