One of the most striking moments in Stranger Things Season 2 is the standalone episode "The Lost Sister." In it, Kali (aka Eight) makes a vision of Matthew Modine's Dr. Brenner from Season 1 appear in the loft to confront Eleven. With the character deceased, as far as we knew, it seemed like a horrific choice for her to do, not to mention the sort of manipulative thing Brenner himself would try. But it also got fans excited for more of the evil genius behind the Hawkins Lab. Will Dr. Brenner be in Stranger Things Season 3? And how would the show find a way to basically un-kill him from the end of the first season?
Personally, I thought this was all nonsense when I first read it, and wrote it off as Reddit tinfoil hat type stuff. Brenner was dead. We *saw* him die. If anything, his appearance in Season 2 was the show's way of demonstrating that unlike Eleven, Kali *hadn't* moved on. She's internalized the lessons of their "papa" far more thoroughly that Eleven ever had. She was, within her rebellion, actually reenacting the behaviors he had demonstrated for them all those years.
But it turns out those who suspected Matthew Modine might be back are actually right.
Speaking to Collider, Stranger Things director Shawn Levy revealed that they have plans for Modine's return in Season 3. He said,
We took a big swing for instance to open the show with a car chase in another city, then Episode 7 goes to another city for an entire episode. Whether or not people feel that episode was entirely successful, the Duffers want to take some swings, and they know that they’re not gonna please everybody. But that feeling of the world getting a bit bigger, especially coupled with the fact that it now seems clear that Brenner is alive, Brenner is out there. I for one think that that one scene with Modine and Millie in Episode 7 is one of the juiciest scenes, and it kind of brought me back to how haunting Modine is in that Brenner role. So, that’s a major unanswered question, and also we’ve now confirmed that Eleven isn’t the only one. There are other numbers.
Episode 7 is, as Levy notes, one of the most argued-over episodes of the season. Some people love it, as it gives Millie Bobby Brown a showcase, and teaches Eleven a lot about herself. Others absolutely hate it, partly because it is an entire hour spent away from everyone else, with a mostly new, one-off cast in a place that isn't Hawkins.
Personally, I think the single episode is an interesting conceit, but the trip to Terry Ives/Chicago for Eleven would have probably played better had it started earlier, and been allowed to interpolate with the rest of the story lines. As it is, the discovery that she's matured beyond Kali, and emotionally worked through her experiences better despite being younger and less worldly, was a good one for the character. Plus, I liked meeting one of the other "laboratory siblings."
However, the visage of Brenner still being alive, or at least giving the production a way to bring him back (a vision Eleven only sees?), is an unexpected twist. Levy also asserted that Season 3 may be leaving Hawkins behind again to meet other of Eleven's "siblings."
[Future seasons leaving Hawkins] is definitely something we’ve talked about. There’s only so much evil that can happen in that lab… [Showrunners] Matt and Ross make the joke that then makes us and the world very uncomfortable, which is eventually, move outta Hawkins! Things are never gonna be great here! But yes, the lab is shut down…
Perhaps going to new labs in new cities is where Eleven will find Brenner again? We'll have to wait and see in Stranger Things Season 3.