Stranger Things Season 5 Volume 2 Reveals What The Upside Down Really Is

The following post contains spoilers for the events of "Stranger Things" Season 5, Volume 2.

In the spirit of David Tennant's Doctor, "Stranger Things" just got timey-wimey with it.

Although the Netflix drama still has a two-plus-hour series finale to release (coming New Year's Eve at 8 p.m. ET), and many lingering questions to answer in that conclusion, the show has at least solved one mystery in the batch of Volume 2 episodes that released on Thursday: What is the Upside Down, really?

At different points in the show's five-season run, its characters thought they had a handle on what the Upside Down truly is and how it came to be. But all of that gets upended in Episode 5 of the current final season, when Dustin makes a massive discovery that not only explains the Upside Down's physics a little better, but also imperils everyone and everything currently hanging out in this bizarro world.

As you'll recall, November's Volume 1 episodes revealed the existence of a massive (and slightly gross) wall in the Upside Down, which essentially spans the perimeter of the entire world and is believed to be the threshold that Vecna crossed with poor Holly Wheeler when she was abducted. In Episode 5 (which dropped Thursday), Dustin theorizes that this wall was created by Vecna's dark magic; in turn, he, Steve, Nancy, and Jonathan roam the Upside Down to find and destroy the shield generator — a "Return of the Jedi" reference — that is likely protecting the wall with its force field-esque energy.

But after stumbling upon some of Dr. Brenner's old notes, Dustin realizes — with considerable horror — that the Upside Down isn't another dimension like he and his friends have been suspecting for all these years. Rather, the Upside Down and its massive, terrifying wall are a bridge between dimensions — between the world of Hawkins and another world that Dustin later coins The Abyss. To destroy the wall would be to destroy the bridge between these two points in time and space (otherwise known as a wormhole), causing the demise of everyone currently on the bridge. So it's not great when Nancy literally shoots the Upside Down's shield generator with a gun, causing the bridge to begin crumbling. (Long story short: She's fine. Everyone's fine. They all make it out of the Upside Down relatively unscathed.)

Later, in Episode 7 — once all of the show's major characters (including a revived Max, yay!) have finally reconvened at The Squawk — Dustin reveals what he knows about the Upside Down being a wormhole that connects Hawkins with The Abyss, adding that The Abyss is where Vecna and all of his monstrous creatures actually live. With a little insight from Max and her recent side quest with Holly, the group deduces that Vecna plans to merge the two worlds, uniting Hawkins and The Abyss and creating a brand-new world that aligns with his vision.

To do so, Vecna needs the minds of the Hawkins children that he's since abducted... but Episode 7 ends just as Vecna is getting the kids' help making these two separate universes into one.

"Stranger Things" fans, what did you think of the show's explanation of what the Upside Down really is? Had you guessed it on your own? Drop a comment with all of your thoughts!