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.

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.

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.

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.

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.

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.

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.

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 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.

El is bullied at school. Joyce opens a mysterious package. A scrappy player shakes up D&D night.

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.

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.