This article contains MAJOR SPOILERS for Stranger Things 5 Vol. 2.
The fifth and final season of Stranger Things dropped a bombshell on viewers tonight when it released its second batch of episodes. At long last, the Duffer Brothers have pulled back the curtain on the true nature of the Upside Down, the eerie reflection dimension beneath Hawkins. This is a revelation they've been teasing for quite a while, and now, it's all out there to break the brains of diehard fans and upend all their carefully planned theories.
However, the explanation for the truth about the Upside Down is so mind-bending that Stranger Things explains it not once, but twice in the three episodes of Volume 2. If you're still struggling to wrap your head around exactly what it all means, don't worry. We're going to get to the bottom of it together.
What is the Upside Down in Stranger Things?
Throughout Stranger Things, the assumption by the characters and audience has always been that the Upside Down is another dimension, which looks exactly like Hawkins except it's home to monsters and is overgrown with creepy tentacles. But in Stranger Things 4, we get a hint that this might not be the case, when Nancy Wheeler (Natalia Dyer) finds a diary in the Upside Down version of her house which reveals that this dimension is a place frozen in time. Everything is exactly as it was on November 6, 1983 — the day that Eleven contacted the Demogorgon, and it subsequently abducted Will Byers.
Now we have a better idea of why that might be. As Dustin (Gaten Matarazzo) learns from Doctor Brenner's notebook, the Upside Down isn't another dimension, but rather a wormhole that connects two other dimensions: our world, and one he dubs the Abyss. The penultimate episode of the series, "The Bridge," is named after the Upside Down, which serves as a bridge between these two worlds and has characteristics of both.
Dustin gives a fun explanation of the Upside Down that his former science teacher Mr. Clarke (Randy Havens) geeks out over: the Upside Down is really an "interdimensional bridge that rips through space-time," which is "wildly unstable" but held together by the exotic matter that the team found floating in the air over the Upside Down version of Hawkins Lab.
The unending, slimy wall that our heroes found in the Upside Down this season isn't a barrier keeping them out of Vecna's hideout; it's the literal edges of the Upside Down wormhole, which we see in full during the opening minutes of Episode 6, "Escape from Camazotz." And now that Nancy shot the exotic matter keeping it all together, the Upside Down is gradually collapsing, which will cut the worlds off from one another once again.
What is the Abyss in Stranger Things?
If the Upside Down is a bridge between Hawkins and another world, obviously we have to talk about that other world. We've actually seen the plane that Dustin calls the Abyss before in the season 4 finale, when Vecna reveals what happened to him after Eleven psychically blasted him out of Hawkins Lab and into another dimension. That dimension was the Abyss, where he wandered until he found the Mind Flayer particles and seemingly bent them to his will.
We're seeing a lot more of this world in Stranger Things 5, and it's enough to confirm Dustin's theory that this world is the place where the Demogorgons, vines, and all the rest of the monsters which have been invading Hawkins came from. I'm expecting to learn more about the Abyss — which was called Dimension X in the play Stranger Things: The First Shadow — in the series finale.
How was the Upside Down bridge formed between Hawkins and the Abyss?
All of this begets a question: how exactly was the bridge formed between Hawkins and the Abyss? Stranger Things has already answered this question, but it did so in such piecemeal fashion that a refresher is definitely in order. I'm hoping the show will make it all more explicit in the series finale, but for now, let's go over what we know.
On September 8, 1979, Henry Creel a.k.a. One (Jamie Campbell Bower) massacred all the staff and children at Hawkins Lab. In the ensuing battle, Eleven banished him from their world, sending him to the Abyss. Doctor Brenner (Matthew Modine) already had a long-standing obsession with finding this other world, which we learn in The First Shadow stems from an encounter his father had with it during World War II. After Eleven booted Henry out of their world, that obsession took on a new form, with Brenner pushing Eleven to try and psychically contact otherworldly beings in hopes of finding Henry.
This went on for years, until Eleven was finally successful on November 6, 1983. On that date, she contacted a Demogorgon, and as we've since learned, the Demogorgons in the Abyss are connected to Henry through the Mind Flayer hive mind particles. As such, when Eleven contacted the Demogorgon, she also unknowingly contacted Henry. It was at this moment that the bridge between worlds was formed.
Where the details get hazy is how exactly that bridge was formed. My guess is that when Eleven and Henry touched minds, that link across worlds created a wormhole between them. The main question is whether this happened automatically on that contact, or whether Henry seized the opportunity to force the creation of the Upside Down once Eleven found him. I'm fully expecting to learn more about the specifics in the Stranger Things series finale, when Eleven and One finally come face-to-face for one last confrontation.
The first seven episodes of Stranger Things 5 are streaming now on Netflix. The Finale premieres on December 31 at 8:00 p.m. ET.