The latest teaser for season four of Stranger Things brings us back to the arc in season two when El finds Kali, another girl who suffered through Dr. Martin Brenner's psychic experiments. In the trailer, we see kids crawling across a rainbow floor and playing chess among other games. A mysterious figure who looks an awful lot like Brenner tells the kids that there's something special planned for them. Then, a voice asks, "Eleven, can you hear me?" The trailer appears to be a flashback, but it could very well be the present day. But one question that you might be wondering is, what happened to the other children at Hawkins Lab?
Let's rewind to episode seven of season two, or "The Lost Sister." Basically, El tracks down Kali, someone who also faced cruel experiments by Brenner's hands. While El can move things around with her mind, Kali has the power to create illusions. After learning how to wield her powers, Kali manages to escape the lab, and she later ends up in Chicago, where she hangs out with a group of misfits and hurts those involved in conducting the experiments. Early in season one, El herself manages to escape Brenner and hide out with Mike Wheeler and his friends. But what about the rest of the children? As the latest teaser indicates, there *were* other children as well.
So what happened to everyone? From their tattoos, we know that El is test subject #011 and that Kali is #008. This numbering suggests that there might be at least ten other children besides El, including Kali. Since Kali is still alive, we can't safely assume that the other children have died. Additionally, since El and Kali's powers differ, the other kids probably have different supernatural abilities, too. And if Brenner is indeed alive, he could be experimenting on a new batch of kids for all we know. It looks like we'll probably find out what happened to the other children in the Rainbow Room come season four.