Eddie Munson, leader of the Hellfire Club, Hawkins High School's Dungeons & Dragons group, becomes a prime suspect in the murders after senior cheerleading captain Chrissy Cunningham dies in his trailer, so Dustin Henderson, Lucas and Erica Sinclair, Max Mayfield, Steve Harrington, Nancy Wheeler, and Robin Buckley begin investigating to clear Eddie's name. They discover that the true perpetrator is a powerful being who resides in the Upside Down, whom they dub "Vecna" after a Dungeons & Dragons character.
Due to the events in Hawkins and the imminent danger to her friends, Eleven goes with Dr. Sam Owens to a secret facility in Nevada to regain her powers, where she is reunited with Dr. Martin Brenner and forced to confront her past in Hawkins National Laboratory with the aid of an isolation tank. The U.S. Military is simultaneously searching for Eleven, Mike, Will, Jonathan, and new friend Argyle in an attempt to reach Eleven before she regains her powers.
Joyce Byers and Murray Bauman venture to Russia upon learning that Jim Hopper may still be alive. Meanwhile, Hopper is held in a Soviet prison camp in Kamchatka, where he and the other inmates, including Dmitri Antonov, are forced to battle a Demogorgon that the Russians have captured.
El is bullied at school. Joyce opens a mysterious package. A scrappy player shakes up D&D night. Warning: Contains graphic violence involving children.
A plane brings Mike to California - and a dead body brings Hawkins to a halt. Nancy goes looking for leads. A shaken Eddie tells the gang what he saw.
Murray and Joyce fly to Alaska, and El faces serious consequences. Robin and Nancy dig up dirt on Hawkins' demons. Dr. Owens delivers sobering news.
Max is in grave danger... and running out of time. A patient at Pennhurst asylum has visitors. Elsewhere, in Russia, Hopper is hard at work.
Owens takes El to Nevada, where she's forced to confront her past, while the Hawkins kids comb a crumbling house for clues. Vecna claims another victim.
Behind the Iron Curtain, a risky rescue mission gets underway. The California crew seeks help from a hacker. Steve takes one for the team.
As Hopper braces to battle a monster, Dustin dissects Vecna's motives - and decodes a message from beyond. El finds strength in a distant memory.
Nancy has sobering visions, and El passes an important test. Back in Hawkins, the gang gathers supplies and prepares for battle.
With selfless hearts and a clash of metal, heroes fight from every corner of the battlefield to save Hawkins - and the world itself.