"Even with the Upside Down, we have a 30-page document that is pretty intricate in terms of what it all means, and where this monster actually came from, and why aren’t there more monsters " says Ross Duffer in the interview. "We have all this stuff that we just didn’t have time for, or we didn’t feel like we needed to get into in season one, because of the main tension of Will."
The story of Will is at the heart of season one, but as fans know, his journey wasn't neatly resolved. The ending of Season 1 suggests that the once-missing boy carries some part of the Upside Down world with him -- or perhaps it was a part of him all along?
"Will’s been there for an entire week, and it’s had some kind of effect on him, both emotionally and perhaps physically," says Ross Duffer. "The idea is he’s escaped this nightmare place, but has he really? That’s a place we wanted to go and potentially explore in season two. What effect does living in there for a week have on him? And what has been done to him? It’s not good, obviously."