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.

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.

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.

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.

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

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.

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.

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.