Picking up literally the day after, on Nov. 13, 1983, Eleven wakes up in the Upside Down and is able to escape back to the woods in Hawkins. Mike begins trying to contact her via his radio. By December, things are back to normal-ish — until Will coughs up a demon slug and realises he's still somehow connected to the Upside Down.
Eleven reveals herself to Hopper, who takes her in. Time skips ahead to October 1984, where new kids, the step-siblings Billy and Max, arrive in Hawkins. Will begins experiencing visions of the Mind Flayer but begs Mike not to tell anyone, and Dustin "adopts" a creature, nicknamed Dart, that turns out to be a baby demogorgon or "demodog." Hopper investigates crop failures that turn out to be concentric circles, while Nancy and Jonathan are warned off of revealing the truth of Barb's death by Owens from Hawkins Lab.