But the series also heralded the return of last season's big bad, a character many presumed to be dead after last being seen in a face-to-face encounter with the Demogorgon.
Spoilers for Stranger Things 2 below…
In an episode in which the character made a cameo as an illusion, the show suggested that Matthew Modine's character Dr. Brenner did not die in the first Stranger Things finale. But the circumstances of the reveal put its veracity into doubt.
"Whether or not people feel that episode was entirely successful, [co-creators] the Duffers want to take some swings, and they know that they're not gonna please everybody," Levy said. "But that feeling of the world getting a bit bigger especially coupled with the fact that it now seems clear that Brenner is alive, Brenner is out there."
In the episode called "The Lost Sister," Eleven (Millie Bobby Brown) is reunited with a fellow experiment subject named Kali (Linnea Berthelsen), AKA Eight. With the power to project illusions into people's minds, Kali and her crew of misfits track down people who worked at the Hawkins Lab to enact bloody revenge.
After convincing Eleven to go along, they find and torture a man who pleads for mercy, offering to give them the location of Brenner in exchange for his life. They are interrupted by the police, and the group is forced to flee before they can find out whether the man was lying or not.
Kali then attempts to manipulate Eleven, causing a hallucination of Brenner in an intense moment that harkened back to their interactions in the first season of Stranger Things.
"I for one think that that one scene with Modine and Millie in Episode 7 is one of the juiciest scenes, and it kind of brought me back to how haunting Modine is in that Brenner role," Levy said. "So that's a major unanswered question, and also we've now confirmed that Eleven isn't the only one. There are other numbers."
With Brenner out in the wild, we'll likely learn more about his whereabouts and how he escaped the Demogorgon in a future season of the show.
Stranger Things 2 is now streaming on Netflix.