Even though the Byers are in California for Season 4, their old house in Hawkins is definitely one of the most memorable in the show, and we all know chaos happens there. From a production standpoint, what was it like to have to constantly trash it?

All the actors are so damn good. They definitely manage to make those characters really come alive for me. For me, that whole group of nerdy friends is so relatable and their stories are incredibly compelling. And I’m so grateful for having been introduced to Winona Ryder — now I can understand why my parents were such fans of her work. But Eleven… wow. The incredible complexity of Eleven is fascinating for me. There are just so many layers to her: the rebel who is so tough and yet so fragile, the girl with unknown origins who is beyond loyal to her friends. Millie Bobby Brown plays her character with absolute perfection. I’ve loved following along, being one of the millions of witnesses watching El grow emotionally, over the past couple years. You’ve said previously that the secret to achieving the show’s look is fastidious estate sale pillaging. How much time do you spend building these worlds? What does it take to furnish an ’80s multiverse? Let’s start with everyone’s favorite alternate dimension, the Upside Down, which is obviously alive and well in Season 4. It may be on a parallel plane, but it also mirrors the characters’ real world. Do you build every set twice — one regular, one dark and demented — or do you create one set and make it all look horrible?From the beginning, I knew that blending our heritage, French stylings and artisanal skills with Stranger Things’ distinctive look was going to work. I told my team that we were going to create the ideal inventory for a special luxury boutique that could have been set inside the Starcourt Mall. We played with ideas that we’ve shown on our fashion-week runways, as well as favorite looks from the series’ different characters. And, of course, we relied on that expert styling, tailoring and embellishment that one expects from Balmain.

We also return to the Wheeler’s basement. What are some things you absolutely must have in an ’80s basement that’s inhabited almost exclusively by teenage boys? And this season, it’s not just Hawkins, Indiana. You’re also set dressing in California. What are some of the key differences in your approach? It was fun. As a production designer, you always hope for a set that is a character in its own right or that goes through some evolution in the course of a season or gets featured in the way the Byers’ house was featured. It's always a lot of work, especially in Season 1 and 2. Both times we were doing these elaborate lights and drawings, [we had to ask ourselves,] “How do we make this space that we're going to spend a lot of time in go through this visually interesting evolution that also is moving the story along?” It's a total pain in the ass in terms of scheduling, because we didn't duplicate that set. We're always working with that same space. It was a real ordeal choreographing with all the departments that are necessary to make those big changeovers, do big lighting changes, change walls out and just physically destroy things. It's a challenge. It's a logistical headache and a continuity nightmare, but ultimately really satisfying because everybody thinks about that set when they think about Stranger Things.That’s easy to answer — the story! Seriously, how could you not be immediately captured by the Duffer Brothers’ genius in storytelling? As soon as each new season is released, I binge, and I love the feeling of being pulled into that amazing, dreamlike world. Balmain creative director Olivier Rousteing is a world-renowned, celebrity-loved fashion designer and one of the youngest people ever to be put at the helm of a major French fashion house. He’s also a Stranger Things superfan, and his love for the show is what inspired Balmain x Stranger Things, a 12-piece capsule collection of pop-infused, ’80s-inspired Balmain shirts, denim and more. The limited-edition collection is available on Nov. 6 in celebration of Stranger Things Day (that’s the day Will Byers went missing in Hawkins, Indiana, in 1983), and fans can shop the exclusive pieces at the Balmain flagship boutiques on rue Saint-Honoré in Paris and Melrose Place in Los Angeles, as well as at Balmain.com. COLLECT 11 STRANGER THINGS FIGURES – Collect all 11 characters from all 4 Seasons of the show, including never-before-seen characters from the new season. Will you find the ultra-rare Demogorgon variant? Then there’s the matter of the Upside Down. While one might assume it’s largely created with the help of visual effects and CGI, the malevolent alternate dimension is actually applied practically to existing set designs, using raw building materials, including foam, plastic and even a healthy amount of pussy willow fluff. The result is an impossibly evil organism that looks like your worst nightmare — but also mind-bendingly mirrors the characters’ reality. We also see the return of many of the show’s iconic locations this season, including the ever-looming Hawkins Laboratories. How do you make an office building look so sinister?