Will Byers was trapped in the Upside Down and has been rescued - but something is still wrong with him.
Eleven (El) closed the gate at Hawkins Lab after the Demogorgon fight; her whereabouts after the school battle are unknown to most of the party.
Mike, Dustin, Lucas, and Will remain a tight friend group with shared secret knowledge of the lab and the monster.
Season 1 ended with the party defeating the Demogorgon at Hawkins Middle School. Eleven used her powers to destroy it and, in the chaos, vanished from their sight. Will was home for Christmas, but a final image showed a shadow-creature rising in his throat - a clear signal that rescue was not complete healing.
The core kids know more than any adult wants them to. Mike is still waiting for Eleven. Dustin and Lucas share the radio-and-bike friendship that carried the search. Will is the quiet center of trauma.
Joyce and Hopper brokered a fragile peace with the lab's secrets: Will's return, Barb's fate, and the need to keep the town from panic. Hopper's cabin life and police role sit uneasily with what he has seen.
Nancy Wheeler and Jonathan Byers have blood on their hands metaphorically - they hunted truth and paid with innocence. Steve's arc bent toward protection rather than popularity.
Will taken to Upside Down; rescued.
Eleven defeats Demogorgon and vanishes.
Christmas shadow shows Will is not fully free.
Season bridge: everything above is end of Season 1. S02E01 ("MADMAX") has not started.
Cutoff discipline: every fact above ends at S01E08. Do not import anything from S02E01 ("MADMAX") or later.