What to know about Stranger Things season 3 before season 4 part 1 hits

polygon.com:

It’s been almost three years since we last got a dose of the Upside Down weirdness of Stranger Things (the same time frame as that between Stranger Things seasons 1 and 3). That sort of delay is not unheard of in the new normal, but hoo boy, there’s a lot to remember about where the folks of Hawkins have been.

Unsurprisingly, things look a lot different for just about everybody in Stranger Things 4. So we’ve put together a refresher on where we left off with Eleven, Will, Mike, Max, Lucas, Dustin, Erica, Steve, Robin, Nancy, Joyce, Hopper — OK, you get the picture.

[Ed. note: There’s gonna be spoilers for Stranger Things season 3 here, as you might’ve expected!]

It’s been long enough you might’ve forgotten: In an homage to the burgeoning mall culture of the 1980s, much of Stranger Things 3’s action takes place at the new Starcourt Mall. Unfortunately, the new shopping complex also happens to be a front for a secret Soviet research base (it was the ’80s!), under which the Russians have built the first Key — a portal to the Upside Down — on American soil. (According to one of the Soviets, there are definitely more in Russia, but none have been as successful as the Hawkins Key.)

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After Steve, Dustin, Erica, and Robin discover the Key, they inform Hopper, who hatches a plan to break into the base and deactivate the machine alongside Joyce and Murray (the conspiracy theorist who gets looped in because he can translate Russian).

Unfortunately, their plan gets hamstrung by Hopper having to fight a Russian hitman to the death right next to the active machine. Unable to rejoin Joyce in the control room before she could stop the machine, the two shared a meaningful glance as she deactivated it, possibly disintegrating