Welcome back to the Upside Down.
If you need a refresher on all the shenanigans that happened inseason 3, EW has you covered.
Here are the most important things to remember before diving into the new episodes.

Finn Wolfhard, Caleb McLaughlin, Charlie Heaton, Sadie Sink, Noah Schnapp, Natalia Dyer, and Millie Bobby Brown in ‘Stranger Things’ season 3.Netflix
Max (Sadie Sink) and Lucas (Caleb McLaughlin) were still together by season’s end.
But at the end of season 3, it seemed El’s powers had been completely spent.
In thetrailer for season 4, she tells someone, “I don’t have my powers.”

Millie Bobby Brown as Eleven in ‘Stranger Things’ season 3.Netflix
Jim Hopper wasn’t the only one to seemingly lose his life last season.

David Harbour as Jim Hopper in ‘Stranger Things’ season 3.Netflix