On November 6, 1983, in Hawkins, Indiana, a scientist is attacked by an unseen creature at a U.S. government laboratory. 12-year-old Will Byers encounters the creature and mysteriously vanishes while cycling home from a Dungeons & Dragons session with his friends Mike Wheeler, Dustin Henderson and Lucas Sinclair. The following day, Will's single mother Joyce Byers reports his disappearance to the police chief Jim Hopper, who starts a search but assures Joyce that almost all missing children are
The boys bring Eleven to Mike's house, where they disagree on what to do. Mike formulates a plan for Eleven to pretend to be a runaway and seek help from his mother, Karen. Eleven refuses, however, revealing that "bad men" are after her. Will's brother Jonathan visits his estranged father Lonnie in Indianapolis to search for Will, but Lonnie rebuffs him. Hopper's search party discovers a scrap of hospital gown near the lab. After recognizing Will in a photograph and demonstrating her telekinesis
Barb awakens in the Upside Down: a decaying, overgrown alternate dimension. She attempts to escape but is attacked by the Demogorgon. Joyce believes Will is communicating through pulses in light bulbs. Hopper visits Hawkins Lab, and the staff permits him to view doctored security footage from the night Will vanished, leading Hopper to investigate Brenner and discover his involvement with Project MKUltra and that a woman named Terry Ives alleged years earlier that Brenner took her daughter. Eleve
Joyce refuses to believe that the body found at the quarry is Will's. Mike feels betrayed by Eleven until she proves that Will is still alive, channeling his voice through Mike's walkie-talkie. The boys theorize that Eleven could use a ham radio at their school to communicate with Will. Nancy notices a figure behind Barb in Jonathan's photo, which Jonathan realizes matches his mother's description of the Demogorgon. Nancy tells the police about Barb's disappearance. She later fights with Steve,
Hopper searches the lab before being knocked out by the lab's guards. The boys ask their science teacher, Mr. Clarke, if it would be possible to travel between alternate dimensions, to which he answers that there could be a theoretical "gate" between dimensions. Hopper awakens at his house and finds a hidden microphone, realizing that Joyce was right the whole time. The boys follow their compasses, searching for a gate that could disrupt the Earth's electromagnetic field. Eleven recalls memories
After finding the small gate, Jonathan pulls Nancy back through it. That night, Nancy is afraid to be alone and asks Jonathan to stay in her bedroom. Steve, attempting to reconcile with Nancy, sees them together through her bedroom window and assumes they are in a relationship. Joyce and Hopper track down Terry Ives, who is catatonic and tended by her sister Becky. Becky explains that Terry was a Project MKUltra participant while unknowingly pregnant and that Terry believes Brenner kidnapped her
Lucas warns Mike that agents are searching for Eleven. Mike, Dustin, and Eleven flee the house while Brenner and his agents chase the kids using vans. Eleven telekinetically flips one of the vans that block their path as the kids escape. Lucas reconciles with Mike and Eleven, and the kids hide in the junkyard. Nancy and Jonathan reveal their knowledge of the Demogorgon to Joyce and Hopper. Hopper learns from Troy that Eleven is with the kids. The kids, teens, and adults all meet at the Byers' ho
Hopper, haunted by the death of his daughter Sara from cancer years earlier, gives up Eleven's location to Brenner, who in exchange allows Hopper and Joyce to enter the Upside Down to rescue Will. Nancy and Jonathan cut their hands to attract the Demogorgon at the Byers' house. Steve, intending to apologize to Jonathan about their fight, arrives just as the Demogorgon appears. Steve, Nancy, and Jonathan fight the Demogorgon and light it on fire, forcing it to retreat back into the Upside Down. M