Season 4 of Stranger Things is coming.

Netflix’s hit sci-fi series is set to return for another season of madness and mayhem in the fictional town of Hawkins, Indiana — and presumably in Russia as well.

Created by brothers Matt and Ross Duffer, the show features an ensemble cast of characters who battle against entities from the Upside Down. The first three seasons have shattered viewership records for the streaming service and been met with critical acclaim.

Here’s everything we know about season 4 so far — from the new cast members to all of the details surrounding the return of fan-favorite Jim Hopper (David Harbour).

Who is returning?
Yes, Jim Hopper is back for season 4 after his fate was left dangling at the end of the season 3 finale, when he seemingly perished to save the town of Hawkins.

Hopper’s return was confirmed in February when Netflix dropped a teaser titled, “From Russia with love…” In the short clip, a snowy scene showed workers constructing a railway line — and one of them was revealed to be a bald Hopper.

Also returning for season 4 is Winona Ryder (Joyce Byers), Gaten Matarazzo (Dustin Henderson), Finn Wolfhard (Mike Wheeler), Millie Bobby Brown (Eleven), Noah Schnapp (Will Byers), Caleb McLaughlin (Lucas Sinclair), Natalia Dyer (Nancy Wheeler), Charlie Heaton (Jonathan Byers), Maya Hawke (Robin Buckley), Sadie Sink (Max Mayfield), Joe Keery (Steve Harrington), Priah Ferguson (Erica Sinclair) and Cara Buono (Karen Wheeler).

Dacre Montgomery will not be reprising his role as Billy Hargrove, who sacrificed himself in the season 3 finale to save Eleven from the Mind Flayer.

Who is joining?
Season 4 will welcome a slew of new characters, including three series regulars: Jamie Campbell Bower, Eduardo Franco and Joseph Quinn.

Bower plays Peter Ballard, “a caring man who works as an orderly at a psychiatric hospital,” Franco plays Argyle, “a fun-loving stoner who proudly delivers delicious pizza pies for Surfer Boy Pizza” in Hawkins, and Quinn plays Eddie Munson, who runs Hawkins High’s official Dungeons and Dragons club.

Joining in recurring roles: Sherman Augustus as Lt. Colonel Sullivan, Mason Dye as Hawkins High popular boy Jason Carver and Robert Englund as Victor Creel, “a disturbed and intimidating man who is imprisoned in a psychiatric hospital for a gruesome murder in the 1950s.”

Plus, two new Russian characters are joining the cast: Nikola Djuricko is playing Yuri, a Russian smuggler, and Tom Wlaschiha plays a Russian prison guard who befriends Hopper.

What will it be about?
Though we do know the name of the season 4 premiere, “The Hellfire Club,” unsurprisingly, the plot itself has remained largely unknown. But given the return of Hopper and two new Russian characters, a storyline in the transcontinental country is to be expected.

In a recent interview with PEOPLE, Harbour teased that in the new season, audiences will “see a lot of your favorite characters doing the thing that you love them for … but you’ll also see them twist it and turn it into other colors and other flavors.”

Harbour also said that fans will “get to see an entirely other color” of Hopper in season 4. “This season is my favorite because he really is going to show you some new colors and what he’s really made up of,” he said.

When will it premiere?
Season 4 of Stranger Things is expected to hit Netflix sometime in 2021, though an official date announcement has yet to be made.

In October, Netflix confirmed that the show had resumed production after filming was delayed due to the ongoing COVID-19 pandemic. The show was a month into production on the upcoming season when the pandemic hit the U.S. in March, with the scripts polished and ready to go, PEOPLE previously reported.

Prior to pausing production, the cast got together in Atlanta for their first table read.

And it’s not the end.
Stranger Things fans can rejoice, because co-creator Ross Duffer has already confirmed that the series will continue past season 4.

“We know what the end is, and we know when it is,” he told The Hollywood Reporter in August. “[The pandemic] has given us time to look ahead, figure out what is best for the show. Starting to fill that out gave us a better idea of how long we need to tell that story.”

“We’ve had a lot more time to work on the scripts,” Matt Duffer added. “For the first time, we have all the scripts written and we’re able to look at it as a whole piece and make adjustments.”