So someone probably already said this but with the theories I have seen on my dash I really needed to address that marker on Twelve’s ‘grave’.
I haven’t seen a lot of people talking about it (although I’m sure the subject’s been thoroughly analysed, but I wasn’t aware of it, hence here I am), but from what I have seen, people seemed to headcannon that Lisa put that marker there because Twelve was special to her, especially dear to her heart.
While that’s pretty cute and sad for the hisalisa shippers, I don’t think that’s the reason she did it.
I don’t believe Lisa would have wanted to physically mark a difference on one of the graves of all these children who died for the same reasons just because she personnally felt more attached to that person. I kind of see that as disrespectful, in a certain way, and I don’t think Lisa would have had that sort of idea. Plus, she knows she isn’t the only one who goes to visit the graves, and that may have also had an impact on that kind of decision.
Also, I think if she had done something special for Twelve, she probably would have done a little something different for Nine at least too (maybe even for Five). That’s just a feeling I’ve got so I can’t really rely on that, but really, I just don’t think that theory fits the character.
What I think that marker may be referring to is the fact that out of the twenty-six children who were part of the Athena Plan, Twelve was the only one who maybe could have lived a normal life.
Twenty-three of the children died in the Facility itself, not reaching more than ten years old. This rules them out since they could not survive the tests.
Five and Nine are a different story. Throughout the episodes, they are seen struggling with strong headaches and physical pain. Five even passes out and ends up at the hospital. They are both suffering, somewhat keeping scars from the experiments practiced on them at a young age. Five may have outlived all the children who stayed in the Facility until the end, but it was pretty evident that the consequences of the tests were going to kill her one day or another.
The same goes with Nine: he escaped, but the aftermath of the tests was just inevitable because the damage was done in his body. It is hinted heavily that their end was drawing close. The end of episode 8, with Nine and Twelve talking about not having enough time, was probably referencing to the fact that Nine could succumb in the following years, months, or even weeks. Maybe days. And the same goes for Five.
The thing is, contrarily to Five and Nine, Twelve never showed any symptoms. Maybe the tests he was subject to before his escape weren’t enough to scar him too badly. And maybe he could have grown up and become a normal adult, without any physical traces of his being part of the test subjects of the Athena Plan.
Therefore, he would be the only one who would not have been denied a life by the experiment, but in fact, he died anyways. This, in my eyes, could be a reasonable motive to make a difference between his grave and all of the others.
Another way of looking at it, though, would be to notice how he was the only one who was really killed, with that specific intention in mind. The children of the Facility died from the experiments, and even if the scientists knew very well that was a possibility, it was not their objective (I am supposing they did want to succeed).
Nine died for the same reasons, years later, succumbing to the headaches. For Five, it’s more tricky, though: she didn’t wait until her body couldn’t take it anymore. She killed herself, unable to suffer through it all anymore (and not finding any more reason to). While the intent here was indeed to find death, I don’t think suicide really counts as assassination.
But Twelve is shot. He doesn’t die from the tests, and he doesn’t decide to give up life. He’s shot in the abdomen by Americans. He is, ultimately, the only one dying from murder. And that also looks like a good reason to acknowledge that Twelve had, indeed, something different from the others.