When it comes to Stranger Things, the most popular number is, rightfully, Eleven. But in another sense, the core number is four.

The Netflix series, which premieres its entire second season Oct. 27, draws from many influences and can cite a number of different origins, but the beating heart resides within the friendship of four young individuals: Mike Wheeler, Lucas Sinclair, Dustin Henderson and Will Byers — played by Finn Wolfhard, Caleb McLaughlin, Gaten Matarazzo and Noah Schnapp, respectively.

In season two, several new figures converge on the small Indiana town of Hawkins, while the older teens and the adults step up to the plate with stories of their own. But the four friends ("The Party," as they often call themselves) are still the driving force of the action: Mike remains relentless in his hope to find the missing Eleven (Millie Bobby Brown), Lucas and Dustin find themselves at odds over the arrival of a new girl in school named Max (Sadie Sink), and Will still struggles with the Upside Down and what he may have brought back into Hawkins from that eerie dimension.

Ahead of the new season, The Hollywood Reporter spoke with all four individually to set the board for what's ahead when their fictional lives go Upside Down again. Read on for their combined thoughts on what to expect from season two.

How would you describe Stranger Things season two and how the show has evolved since the first season?

Finn Wolfhard (Mike): It's the same tone, generally. The main difference is that it's on a bigger scale. We have more access to doing more drama and horror and stuff.

Gaten Matarazzo (Dustin): It's hard to describe it, because there's just so much going on...there are so many different genres within the show and so many cool new characters. It's hard to pinpoint a specific mood for the second season. I'll say that it's darker and a little scarier.

Caleb McLaughlin (Lucas): Season two is a lot darker. It puts a lot on your spirit. It takes place after the finding of Will, from where he was in the Upside Down, where you saw him in the last episode of season one and he was throwing up this slug into the sink. Everyone knew it came from the Upside Down. It moves from there. We all see what happens to him — the aftermath, and how it affects everyone in the town.

Noah Schnapp (Will): Season two is a lot like season one, but it kind of goes a different way than the audience might expect. I see it as a lot more intense than the first season. I have a much bigger role this season, where you'll see how Will is dealing with the Upside Down and how it's changed him. Is it changing him for the worse, or is it changing him for the better? How's he dealing with his family and friends?

Was it a very different experience filming season two, since Will was missing throughout season one?

Schnapp: It was a very different experience! The first season, I was in and out. I wasn't even really there the whole time. I didn't get to have the full filming experience. I didn't get too close with any of the crew, because I wasn't really there. The second season, I was lucky to get to be there for the full year. I was able to film with everyone and be there every day. It was a lot of fun to get into that routine. Everyone's so nice. It's a big family.

McLaughlin: It was cool! Last year, we knew he was part of the gang. But now? He's officially part of the ST Squad!

Wolfhard: We never even counted Noah out of the crew in the first season. It's just that we didn't see him that much. Now he's fully a part of it. We're so happy that happened. He kills it this season. He killed it last season, even with the small scenes he had. But we're so excited to see how it's going to progress on the show. It's going to be amazing.

What's ahead for your character this year?

McLaughlin: Lucas is there for [Will]. He's there to see how he's doing. He hasn't seen him in a while. Will went to another dimension and was the only one who survived. He's going through a lot. Lucas knows now that there's more than just the scary bears and coyotes out there in the woods. There are Demogorgons! His expectations of the world are different now.

Matarazzo: All of the boys are trying to cope with what happened [to Will] a year ago, and Dustin's looking toward certain new characters to try to heal the group — and himself, in a way.

Wolfhard: Mike's sort of a loner. He isn't really impressing anyone anymore. He kind of just feels bad for himself, and slowly, as the season progresses, he gets back into his leader ways because of what's happening with Will.

Schnapp: No one knows what to do with Will. No one's really experienced this before, with Will being in the Upside Down. He was in another dimension. He was gone. Everyone who knew about it was very confused. Now that he's back...has something happened to him? Is something inside of him? Everyone's questioning that about him, and you learn more about that as an audience member.

And he has a new nickname as well: "Zombie Boy."

Schnapp: Yeah, he doesn't like that. Will himself really wants to fit in with his friends again and go back to his normal life, playing D&D and biking around. Being called "Zombie Boy" doesn't let him fit in like he wants to.

The new missing member of the party is Eleven, who disappeared at the end of season one. How will that impact the season?

Wolfhard: It's not even an up and down thing...Mike honestly doesn't even know if she's alive or dead. He knows deep down that she's still out there. She's the first person he ever fell in love with. It's hard to roll that back. It's hard to leave that alone for the rest of your life. He's struggling.

What can you say about the newest member of the group this year: Max, played by Sadie Sink?

McLaughlin: When [the Duffer Brothers] said there was going to be a new person, at first I was like, "What? Huh? Why?" I didn't know who it was going to be, but then once she was cast, I was like, "Oh! Sadie! I know her!" She was on Broadway like me and Gaten, so I knew her from that, and I knew her family. She was in Annie when I was in Lion King. All of the Broadway kids would meet up at a park in New York City and we would hang out. It was cool to know somebody who I knew we would all get along with.

What can we expect from Max as a character?

McLaughlin: She won't change the whole groove of Stranger Things or the kids. She'll actually add to the creativity of the kids. She's cool. She's a tomboy. She's going to fit in very smoothly.

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