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.

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.

Dr. Brenner holds Hopper and Joyce for questioning while the boys wait with Eleven in the gym. Back at Will's, Nancy and Jonathan prepare for battle.

Eleven makes plans to finish what she started while the survivors turn up the heat on the monstrous force that's holding Will hostage.

An unlikely hero steps forward when a deadly development puts the Hawkins Lab on lockdown, trapping Will and several others inside.

Terror reigns in the food court when the Mind Flayer comes to collect. But down below, in the dark, the future of the world is at stake.

Will's connection to a shadowy evil grows stronger, but no one's quite sure how to stop it. Elsewhere, Dustin and Steve forge an unlikely bond.

With selfless hearts and a clash of metal, heroes fight from every corner of the battlefield to save Hawkins — and the world itself.

Eleven struggles to reach Will, while Lucas warns that "the bad men are coming." Nancy and Jonathan show the police what Jonathan caught on camera.

Refusing to believe Will is dead, Joyce tries to connect with her son. The boys give Eleven a makeover. Nancy and Jonathan form an unlikely alliance.

A code red brings the gang back together to face a frighteningly familiar evil. Karen urges Nancy to keep digging, and Robin finds a useful map.

An increasingly concerned Nancy looks for Barb and finds out what Jonathan's been up to. Joyce is convinced Will is trying to talk to her.

A frantic Jonathan looks for Nancy in the darkness, but Steve's looking for her, too. Hopper and Joyce uncover the truth about the lab's experiments.

Nancy and Jonathan swap conspiracy theories with a new ally as Eleven searches for someone from her past. “Bob the Brain” tackles a difficult problem.

With time running out -- and an assassin close behind -- Hopper's crew races back to Hawkins, where El and the kids are preparing for war.

Hopper breaks into the lab while Nancy and Jonathan confront the force that took Will. The boys ask Mr. Clarke how to travel to another dimension.

Nancy has sobering visions, and El passes an important test. Back in Hawkins, the gang gathers supplies and prepares for battle.

On his way home from a friend's house, young Will sees something terrifying. Nearby, a sinister secret lurks in the depths of a government lab.

Dustin adopts a strange new pet, and Eleven grows increasingly impatient. A well-meaning Bob urges Will to stand up to his fears.

An ailing Will opens up to Joyce -- with disturbing results. While Hopper digs for the truth, Eleven unearths a surprising discovery.

Strange surprises lurk inside an old farmhouse and deep beneath the Starcourt Mall. Meanwhile, the Mind Flayer is gathering strength.

Dr. Alexei reveals what the Russians have been building, and Eleven sees where Billy has been. Dustin and Erica stage a daring rescue.

Behind the Iron Curtain, a risky rescue mission gets underway. The California crew seeks help from a hacker. Steve takes one for the team.

Lucas, Mike and Dustin try to talk to the girl they found in the woods. Hopper questions an anxious Joyce about an unsettling phone call.

After Will sees something terrible on trick-or-treat night, Mike wonders whether Eleven's still out there. Nancy wrestles with the truth about Barb.