As the town preps for Halloween, a high-scoring rival shakes things up at the arcade, and a skeptical Hopper inspects a field of rotting pumpkins.

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.

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.

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.

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.

Psychic visions draw Eleven to a band of violent outcasts and an angry girl with a shadowy past.

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

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

Summer brings new jobs and budding romance. But the mood shifts when Dustin's radio picks up a Russian broadcast, and Will senses something is wrong.

Nancy and Jonathan follow a lead, Steve and Robin sign on to a secret mission, and Max and Eleven go shopping. A rattled Billy has troubling visions.

With El and Max looking for Billy, Will declares a day without girls. Steve and Dustin go on a stakeout, and Joyce and Hopper return to Hawkins Lab.

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.

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.

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.

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.