It is November 16, 1983 in Hawkins, Indiana. Inside Hawkins National Laboratory, a scientist bursts out a door, running from something that isn't there. He runs to the elevator, tapping the floor button repeatedly, looking back and forth. He then gets in and taps the button again. He looks forward then up slowly, as he hears and sees something that we can't see. He is then pulled up as the elevator doors close, yelling loudly.
We then see the Wheeler residence, as four friends--Mike Wheeler, Will Byers, Dustin Henderson, and Lucas Sinclair--play Dungeons & Dragons. We then see that the Demogorgon is played, as Will is pressured to cast Fireball. He rolls the die but it lands on the floor, with the group scrambling for it. Mike is then called by his mother, Nancy, to end the game. Meanwhile, the trio find it, but it is a 7, as only a 13 or higher can cast a Fireball, which means Will was eaten. Will then leaves, after telling Mike that it was a 7.
Will rides his bike through the woods, passing by Hawkins Laboratory. He then sees something weird in front of him, as he accidentally falls down a steep hill and crashes. He then abandons his bike and runs to his house. He unlocks the back door to find nobody home, as the thing out back is probably chasing him. He tries to call his parents, but only weird breathing is heard. Something then unlocks the bolt on the door. Will then runs to the shed in the backyard, where he sees the thing. The light glows brightly and then fades, revealing no one there anymore.
The next morning, November 17, Police Chief Jim Hopper wakes up shirtless. He then walks outside, enjoying the view and then prepares for work, smoking a cigarette. He then leaves.
Will's mother, Joyce, and his brother, Jonathan, are arguing about if Will ever came home. It is then revealed that both were working; Jonathan took the night shift. Joyce then calls Nancy, and then asks if Will went home, she replies that he left around 8:00. They all conclude, including his friends, that Will probably left to go to school early. As they arrive, the trio are then bullied by Troy, the class bully, and an accomplice. Dustin is then picked on because of his condition, cleidocranial dysplasia, and his ability to flex bone. Lucas and Mike then acknowledge his ability.
Two students, Nancy Wheeler, Mike's sister, and Barbara Holland, Nancy's friend, then discuss before school. Right after, Nancy's boyfriend, Steve, and she start making out in the bathroom. Nancy has to leave, while Steve asks if she would like to go anywhere, but she declines, having to study for her test. He then asks to come over at 8 pm, to which she reluctantly agrees.
Hopper then arrives at the police station. The assistant, Flo, tells Hopper that Joyce can't find her son. Drunk, he ignores Flo, but goes anyway. He then types a police report on Will, labeling him as "missing." Joyce and Hopper don't instantly find a solution, as Joyce is trying to engage with him in a conversation, while Hopper is being unreliable.
Three people then arrive at the Laboratory, where they are greeted by Dr. Martin Brenner, one of the Lab's key scientists. The four then put on hazmat suits, and go down the elevator to a dark room. While looking, they see black roots and flesh-like substances on the walls. They then come across a giant flesh-root substance on the wall. One of them asks about a girl; Brenner replies, "She can't have gone far."
A girl wearing a hospital gown and with a shaved head is then seen walking through the forest, alone. She sees the owner of a restaurant walk out, and decides to go there. She enters without notice, but as soon as she eats the food, the owner comes and tries to stop her, but is surprised. Hawkins Middle School then ends. Dustin, Lucas, and Mike then ask one of the teachers, Scott Clarke, if the Heathkit Ham Shack radio had arrived. He says yes, due to them being prime members of the AV club. A school staff member then asks for them, as they are being questioned for the disappearance of Will. They are told to not investigate, for their safety.
Joyce then goes to look for Will at his fort in the forest, Castle Byers. She then remembers getting him tickets to see the 1982 film Poltergeist. But in reality, he is nowhere there at all. Jonathan is there looking for him as well, both calling out to him. Meanwhile, the restaurant owner feeds the mysterious girl. He asks him if she escaped, to no answer. He then takes the food and asks her for her name, she replies "Eleven" after he asks what the tattoo "011" means. He then gives back the food and calls authorities to identify her. She then sees a fan and consciously stares at it; it stops.
Hopper and his team then find Will's bike where it was, exactly in the same position. Brenner and others are then shown at the Laboratory tapping in on conversations. We then switch to Joyce trying to reach her ex-husband, Lonnie, but his girlfriend, Cynthia, answers and hangs up. She then calls a neighbor, but the answering machine beeps. Hopper then arrives and gives them Will's bike, and he reveals evidence that Will came home. The family dog then barks at the shed, while Hopper investigates. He finds something behind a shelf, and the light blinking until one of his deputies come in, scaring Hopper. He then announces a search party for them to announce to the citizens.
Mike and his family start fighting over investing for Will, but his family says "No" by default, but his father enrages him and his mother, Karen. The search party is then shown in the forest. Hopper and Mr. Clarke then exchange a conversation regarding WIll, and then Sarah, her daughter. Clarke is then informed that her daughter had died long ago, with the saying "lives with her mom in the city" implies that she is buried there.
Mike and Lucas then discuss over the comm radios that they have. Mike suggests that Will might've put himself in danger to protect the trio, instead of protecting them, leading to apparent sacrifice. Lucas and Mike then resolve to meet each other at 10. While Mike leaves, he sees Steve climbing the window to Nancy's bedroom, with her soon closing it. The owner, Benny Hammond, and 011 then exchange a little conversation, before Agent Connie Frazer, disguised as though she is from Social Services, arrives. 011, looking from a distance, sees Frazer shoot Benny in the head, killing him. She then kills two agents and escapes through the back door.
Dustin, Lucas, and Mike are then going down the back road, Mirkwood. They cross the restricted area of the woods, with Mike telling Dustin to stay on channel 6, and to not do anything stupid. Steve and Nancy are then shown studying, with him reading index cards that Nancy needs to give answer to. Steve then suggests to strip off clothing for each one if Nancy gets it correct/incorrect. After she answers one wrong, they make out again on the bed, with Nancy asking if he was in it just for sex. He replies no, and then jokes around before getting back to studying.
Joyce and Jonathan are then back at home on a bed, mourning over Will and his disappearance. Jonathan then remorsefully regrets that he should've been there for Will, which she tells him not to worry about it because it is not his fault. She then gets a mysterious phone call from, what we believe, Will, but it shorts out after she asks the unknown caller, "What have you done to my boy?", to which there is no one on the phone. They then try to console each other.
Dustin, Lucas, and Mike then are shown going through the forest. They hear rustling and then see 011, to their surprise. They decide to take her to Mike's house, where they ask her miscellaneous questions. Mike then observes that she is scared and cold. She tries to change out of her wet shirt, but the trio are disgusted because of gender. Mike directs her to the bathroom, where she changes. Dustin and Lucas thinks she is paranoid, but Mike stays sane, telling them to keep it a secret. Mike then offers 011 a sleeping bag, where he nicknames her "El." They both then sleep.
On November 18, Joyce and Jonathan discuss xeroxing a missing poster for Will when Hopper arrives, telling Joyce that Will hasn't been found, to her anger. She discusses the "phone call," with Hopper dismissing it as a prank albeit her pleads. Jonathan offers to go to Lonnie's instead of Hopper, but he says no instantly. Mike then tells El to get help, but she says no and implies "bad people" who want to kill her. Brenner then listens to Joyce's 9-1-1 call; the search party is still unsuccessfully looking. Steve then invites Nancy for a party, to which she agrees, but they react toxic toward Jonathan and Will.
Dustin and Lucas, at school, don't see Mike, staying home to look after El. Jonathan, putting on The Clash's "Should I Stay or Should I Go?", remembers him and Will listening to it as he drives to Lonnie. Joyce, however, buys a new phone for free due to Jonathan having her money. A handyman, an agent for the Laboratory, verifies that the Byerses aren't home, as they see ooze dripping from the shed's walls. Meanwhile, while Max is showing her Yoda, El remembers being locked by Brenner into solitary confinement, with her calling him "Papa," confirming that she is the girl that he and others talked about before. She also recognizes Will when Mike shows her a picture of him.
Meanwhile, Joyce sets up the new phone and waits for another call. Hopper investigate Benny's death, placed falsely like a suicide. Meanwhile, Jonathan visits Lonnie, confirming that Will is not there but that he is drunk. Jonathan angrily gives him the missing poster for Will due to his arrogance and drunk behavior. Lucas and Dustin angrily attempt to tell Karen about El after finding out that he spent all day with her, but she locks the door without arms, revealing her psychokinesis as well as a nosebleed.
Hopper goes to the station to talk to the customer that was there when 011 arrived, he gives slight information but not enough to consider it other than a suicide, but he gives information on El, which Hopper mistakes for Will. Meanwhile, Karen and family, along with Mike, Dustin, and Lucas all have dinner. They are acting weirdly to contain the powerful surprise that kept them in. El then walks by, when Karen hears something, but Dustin fakes a spasm to successfully draw attention away. Meanwhile, the search party looks for Will, mistakenly for El, where they find the tag of El's hospital gown in one of the Laboratory's drain pipes. They then find the fence of the Lab.
El, playing with Mike's radio, is given leftovers by Mike, where he gives the definition of friend, and a spit swear by Lucas. Barbara and Nancy then arrive at Steve's house, but Barbara is suspicious since two of Steve's "friends" had sex since seventh grade. Hopper wonders suspiciously about the events: The last missing person was in summer '23 and last suicide was in fall '61, long ago. El, later that night, tells them that Will is somewhere else, hiding from something terrible, characterized by the Demogorgon.
Jonathan, with his camera, takes pictures of the scene near Will's bike. He hears screaming; he runs to find Steve and the others drinking and swimming, taking pictures of it, including Nancy having sex with Steve. Joyce then gets another "call" from Will, but it shorts again. "Should I Stay or Should I Go?" then starts playing in the house, with Joyce believing it a message, encountering something trying to go through the wall, but returns when music plays. Barbara, having cut her hand with a drop of blood in the water, is then taken by something outside, leaving nothing.
Barbara wakes up in a place similar to the pool, but it is empty, everything is covered in black root, and it's cold. She is later dragged down by a creature, which appears to be an abnormal man with no face. Nancy, having sex, cannot seem to hear her as she is dragged down.
Nancy, realizing that she is late, gets in trouble with Karen but she pushes her away, not letting her connect to her at all, stating that "nothing happened." Jonathan, after trying to communicate with Will via lights, tells her to stop. Simultaneously, Dustin, Mike, and Lucas prep to look for Will again, but go to school. Before leaving, Mike tells her to be there at 3:15; she repeats it as "Three-One-Five." Hopper, during the morning/afternoon, goes to Hawkins Laboratory and after an incident, is let in to investigate the drain via security tapes unsuccessfully. El, during this, watches a Coca-Cola commercial, flashing back to the Lab: Hooked up to an electroencephalograph machine, she crushes an empty Coke can with telekinesis, having a nosebleed after.
On November 19, Joyce, finding Christmas lights, decides to set up an intricate system to indicate Will's position, but runs out. She stocks up on them at the store, and decides to check. Meanwhile, Hopper is convinced that they are lying, as there was rainy weather. That didn't show up on tape. Brenner and two other people send a man through the fleshy substance in the Laboratory, revealed to be a portal. He documents what he sees, but is then killed by the creature, leaving only the bloody tether.
Jonathan, later, decides to enlarge the photos he took, but is spotted by Nicole, one of Steve's friends, who ambush his car, rip the photos, and break his camera desperately. Karen then visits Joyce for dinner, eating her casserole, but her 3-year-old toddler, Holly, sees lights leading into Will's room, where the monster tries to enter. At the same time, Hopper researches anything Hawkins Laboratory-related. Nancy, worried about Barbara's disappearance, calls her mother.
While at the power lines, El has a flashback of her strapped to the machine again to attempt infliction on a cat, refusing. As she is about to be locked away, she slams one guard against the wall and snaps another's neck, killing both. Brenner sees this and calls it "incredible." El then meets up with Lucas, Dustin, and Mike as they travel to find Will again, as Mike bonds with El, telling her about Troy tripping him. Later Nancy finds Barbara's car and goes to Steve's house, only to find the creature and escapes.
Back at the Byers residence, Joyce finds the Christmas lights leading her to a hidden drawer. Grabbing a set of unplugged Christmas lights, she asks, "Will, are you here?" They glow mysteriously once. She tells him to blink the lights once for "Yes," twice for "No," asking him, "Are you alive?", to which the lights blink immensely once. She then asks, "Are you safe?", to which the lights immensely blink: Twice. Will is then lost as the lights don't blink anymore. She then paints the alphabet on the wallpaper, and hangs a light above each letter to create more complex messages. Hopper, with another deputy, search through the library, finding out that the Laboratory is CIA-sanctioned and being called to the quarry. Just around the same period, El lead the trio to Will's house, stating that he's "hiding" there, which helps her become accused of lying by them. Suddenly, Dustin sees a police cruiser and ambulance, following them.
Joyce, finishing the project, then asks "Will" where he is. The lights slowly spell out the sentence, "Right here." Joyce, now confused and scared, asks Will what she should do as to finding him. The letters then slowly, and musically intensely, spell, "Run." Just as the monster enters, Joyce looks behind to find it breaking through the wallpaper and runs out.
Following the cops, Dustin, El, Lucas, and Mike end up at the quarry. At the same time, Joyce runs into Jonathan and hugs him. Mike then snaps at El for lying, and leaves. He arrives home, and hugs Karen very sadly. Hopper watches emotionally as well as the others as Will is pulled out of the water. Dead.
Hopper then comes to Will's home, where he finds a scared Joyce with the letters on the wall, with her describing the creature that came out of the wall as "almost human but it wasn't. It had these long arms and it didn't have a face." Hopper thinks she is experiencing grief, and tells her the aftermath following Sarah's death, but Joyce finds it completely irrelevant. He warns her to get some sleep, and encourages her to look at Will in the morgue. Instead, she arms herself with a ax and stays awake.
Mike, upset with El over Will's "discovery," tells her that she did something that "sucks" and that Lucas was all along right about her. However, she tunes the radio to Will's presence, being able to hear but not speak to him, and hears him singing. However, it is only seconds brief, but it gives Mike proof that Will is alive.
On November 20, at the morgue, Jonathan leaves at the sight of Will, but Joyce asks for proof of the birthmark on his right arm, cutting to Hopper. Hopper ensures Jonathan that Joyce will be fine, and everything will be alright. Just then, an enraged Joyce walks out, refusing to sign the documents. Jonathan then yells at her that Will is dead, parting ways soon after an audience appears.
Nancy, after school, tells Steve that she went back to look for Barbara, but to no avail. She also details the monster had no face, same as Joyce's description. However, Steve is worried about his accusation by his parents while Nancy is focused on Barbara. She then leaves angrily. El then tunes to Will again, but he sounds different: All decide to disguise El to get her to Mr. Clarke's Heathkit. Later, Nancy is interrogated by Hooper and a deputy, giving some false information that was verified by the police with real.
The trio take El to school and try to sneak into Mr. Clarke's room, but are discovered by him soon later. He negotiates a deal soon after that if they attend a assembly honoring Will Byers, he will let them use the Heathkit the rest of the day, to which they accept. During the assembly, however, Mike sees Troy laughing at his funeral and confronts and then pushes him. However, before he can attack, he is stopped by El and urinates on himself, to the school's humiliation. Meanwhile, Nancy discovers the monsters on one of Jonathan's ripped photographs and explains it to him, who realizes that his mother was right. Hopper then interrogates the man who found Will, saying that someone didn't want anybody getting close to the body.
El is taken to the Heathkit, where she remembers from the Lab that she was told to listen to a certain man via her own mind. WHile Dustin, Lucas, and Mike watch, the light burns out as they listen to Will engaging in a conversation with Joyce. However, at the same time, after Will disappears, Joyce hacks a hole in the house and the frequency fries the Heathkit, suffering another nosebleed. Nancy and Jonathan then enlarge and brighten the ripped photo, giving clear evidence of the monster and the possibility of Will and Barbara's existence. Hopper then breaks into the morgue and knifes open Will's body, which reveals in it a stuffed, life-like doll of Will. Lonnie then arrives to ensure Joyce's safety. Around the same time as well, Hopper breaks in and discovers the lab's gate, and possibly El's bedroom, but is knocked unconscious. Lonnie intoxicates Joyce with alcohol, and tries to convince her to let Will go; Jonathan arrives and asks him to get out, but he refuses and scrutinizes him for also getting caught up in Joyce.
Lucas, Dustin, and Mike discuss about Will's existence, as Mike brings up El's leading towards Will's house, flipping the Dungeons & Dragons game upside down, and the symbolism of the bottom board: They discover that Will himself is trapped in the "Upside Down": The Vale of Shadows, a "dark echo" of our habitable dimension that is uninhabitable, dark, decaying, and deathly, plus filled with monsters: an alternate dimension. Hopper then wakes up in his home. Sensing something suspicious, he tears apart every appliance and finds a microphone in the light-bulb fixture, his house being bugged after he arrived. Everyone attends Will's funeral, as everyone pays their respects. Joyce then remembers Will drawing a mythical figure, a "wizard" that can shoot fireballs, but she comments on the fact that they are green because the red crayon is missing. Later, Brenner and other scientists listen to the trio with El at the Heathkit.
Jonathan and Nancy grab a revolver from a nearby car at the funeral to devise a plan. At the funeral, Dustin, Lucas, and Mike ask Mr. Clarke about interdimensional travel, in which he gives "the flea and the acrobat" theory: An acrobat on a tightrope can go forward and backward, but a flea can go the same but sideways and upside down, but a gateway can be created by using energy to rip a hole in space-time. He also gives signs of a gateway: the disruption of the electromagnetic field, which would affect compasses, the environment, and numerous others. Soon after the funeral, Lonnie removes the Christmas lights and boards up the hole. At the same time, Dustin discovers the compasses are not pointing true North; they are disrupted by the gate's energy, drawing the compasses towards it, confirming Clarke's theories. Lonnie then admits that he planned the funeral for finance, using Joyce.
The trio, along with El, walk in the direction of the compass to the portal. Along the way, El has a flashback: Using a sensory-deprivation tank and hooked to the wave machine, they use her to collect information from a Russian man. Realizing something, she asks Mike to turn back, refusing to do so, as they continue their trek. Around the same time, Nancy and Jonathan walk in the forest but both argue as well, damaging their relationship towards one another. Hopper then arrives at the Byers home, shushing her in case of her home being bugged, but he can't find the device after looking, admitting that she was right all along.
At the junkyard hangout, the compasses suddenly turn back home weirdly. While trying to figure out what is going on, Lucas blames El due to her telekinetic abilities. Looking at her sleeve, he sees blood, fresh evidence that El used her powers, which she admits as "not safe." Lucas and Mike then fight, during which El telekinetically knocks out Lucas by flying him onto a metal plate. Mike then snaps at El for doing so, and she escapes. She then flashes back to finding the Russian, where she "casts Shadowwalk"--projects herself on the astral plane to locate people--on him, but finds the monster and it gives chase. Lucas then heads home, angered and sad.
Nancy, still walking in the woods with Jonathan, hears something. They both find a severely wounded deer in the woods, possibly hit by a car and whimpering in pain. Jonathan then loads the gun to euthanize the deer under Nancy's suggestion, but it is taken away by the creature. They then find a trail of blood left by the deer; however, Nancy tracks it to a separate gate under a tree and goes alone. She ends up in the Upside Down, finding the creature eating the deer. She backs away, but she steps on a root which attracts the creature. She screams as she runs away, with Jonathan unable to find her as the gate closes. But at the last second, Nancy is pulled out by Jonathan before the gate closes and the monster can get her.
Steve, along with his friends, pay a visit to Nancy's House. However, as he climbs her windows, Steve sees Jonathan putting a towel on Nancy and comforting her, which he ultimately mistakes as cheating on him. Nancy, after encountering the monster, is intensely scarred and frightened, asking Jonathan to stay with her for company. She asks him to sleep with him on her bed, but that's about the only thing that's a little bit sexual. The next morning, she finds her upright and sleep-deprived, and both decide to kill it finally.
Mike, lonely and sad, remembers El's spot before he furiously kicks it in, depressed. Meanwhile, Hopper tracks down Terry Ives, the woman claiming to have her daughter taken, address. At her house, Nancy and Jonathan late the monster's location will Barbara and the deer's last locations, finding an average distance of a mile or less, finding that it can smell blood, and they sneak out of the house to buy weapons at an army surplus store.
Frazer, disguised as a newsletter editor, offers participation of students to a weekly AV "newsletter" to Clarke, with him giving the names of Dustin, Lucas, and Mike to her. Dustin, arriving at Mike's place, contemplates on reconciling with Lucas by shaking his hand, a sign of forgiveness from whoever "drew blood" or started a fight first. Dustin then packs his and Mike's stuff to get Lucas.
El has another flashback: Brenner tells her that "today, we make contact." She then wakes up from apparent sleep with no wig on. She puts it on, but decides to take it off. She then screams at a nearby lake, which violently ripples the water and scares off a birds. Meanwhile, Karen discovers that Nancy is missing. At Lucas's, he decides to shake Mike's hand under a condition that they forget 011, and they go straight forward. Lucas disagrees as to El, but Mike believes that El was protecting them. They end up disagreeing completely, and Lucas decides to fly solo while Mike travels with Dustin. El, however, enters a grocery store, getting another flashback; Brenner introducing her to colleagues, where she is lowered to apparently find the monster. She then steals Eggos, slamming the sliding doors violently in front of an employee calling her out. The duo notice this and travel in the direction that she most likely went, with a stranger watching from afar.
Joyce and Hopper travel to Terry's home, where they find her fixated on a small TV, unable to speak or move. Her sister explains that she studied in MK Ultra training at the Laboratory in the '50's; she would be drugged, stripped and put in isolation tanks, sensory-deprivation ones to try to improve the brain's functions. She apparently "miscarried" a daughter in the third trimester: Terry imagined her, Jane, as a "special" daughter with "abilities," matching 011, revealing that she was captured by Brenner, who faked her death, as Terry's sister completely disbelieves.
Lucas, on his bike, arrives at the fenced area of the Hawkins Laboratory. He looks at it in disgust, and takes his bike to the left for open space. Meanwhile (again, really?), Nancy and Jonathan stock up on weapons and traps at the army surplus store. The cashier asks, "What you kids doin' with all this?" Nancy replies, "Monster hunting," to the cashier's disbelief. Jonathan and Nancy load the supplies into Jonathan's car. As they talk toward one another, suddenly a car passes by with a man saying, "Can't wait to see your movie." The duo then run to a local movie theater, with the words half written/half spray-painted on the marquee: "ALL THE RIGHT MOVES STARRING NANCY THE SLUT WHEELER." This causes Nancy's reputation to decline drastically, as both adults and teens start looking at her weirdly and denouncing her.
Nancy then finds the culprits: Steve and the gang, with Tommy spray-painting all of the words. Nancy slaps Steve as the friends jeer at her with the fact that they're toxic, so that's why. Jonathan then shows up, with the Steve gang denouncing him and his family while jeering at his actions for seconds, when instantly Jonathan whirls around, grabs Steve, and decks a two-pound iron to the face making Steve fall back. He then grabs Jonathan and knocks him to the ground as they then start fighting, with Steve's friends telling him to stop, but Jonathan then gains the upper hand, decking his face repeatedly into submission. The cops then try to get him, but he punches one instinctively, leading him to be arrested, but with Nancy's reputation dealt a hard blow.
Hopper and Joyce then leave as Joyce looks at Terry one last time. As they get into the car, Hopper reassures Joyce that they will find Will, self-checking and knowing themselves that 011 is actually Jane Ives, Terry's long-lost daughter whom they thought was dead. Hopper is then called by the police to go to the department and sort out Jonathan. Nancy is offered to leave by one of the staff, but she is also called out by her for her "actions" and decides to stay with Jonathan to console him.
El, with the Eggos waffles, eats in the woods while Mike and Dustin call out for her. Just then, they spot Troy with a knife, and the duo then bolt for it with Troy right behind. Meanwhile, Lucas then finds the compass needle pointed in a general direction of a tree, climbing up it and using binoculars to spot the gate, but finds three men entering and an armed vehicle, as well as handyman vehicles that say "Hawkins Power and Light," which Lucas saw with one agent earlier. At the same time, Mike and Dustin run up a cliff just above the quarry. While trying to defend themselves, Dustin is held captive by Troy, threatening Mike that he will cut out Dustin's teeth with his knife unless he jumps off the cliff into the quarry, which would almost certainly be fatal for him. Mike, under pressure from Troy, jumps off but he is levitated back onto the cliff by El, who pushes away Troy's accomplice and breaks Troy's right arm before they leave. She then collapses.
El remembers being in astral projection when she finds the monster eating on something. She silently walks up towards it, and touches it one time. It then turns around towards her, scaring her to the point that she uses her powers accidentally to open up the gate. Waking up, she sees Mike and admits that she opened the gate, tearfully admitting that she's "the monster." Mike, however, tells her that she saved him and that it's what really matters Mike, Dustin, and El all then do a group hug.
Mike and Dustin then grab their bikes along with El as they go home. An agent, disguised as a handyman in a truck, then tells the Laboratory that they are heading home. Agents then quickly load up, as Brenner and his group of agents, all armed, leave in a handyman car. Lucas, still up in the tree, realizes that the agents are going to Mike's home, just as Mike, Dustin, and El arrive.
Mike removes the makeup from El, answering from her question, that she is still "pretty." He then also says that he's happy that El is home, to which she also contemplates the same thing. They are about to--apparently--kiss, but Dustin interrupts saying that "It's Lucas. I think he's in trouble." They tune Mike's comm radio albeit being out of range by a long shot, to which he says that "they know about Eleven" and that "the bad men are coming," while biking down a street to warn them. While most of the transcription is muddled, they understand "bad men" and check outside, telling Karen that they are leaving, and the trio depart with their bikes just as Brenner spots them.
Dustin, through his comm radio, transmits to Lucas and tells him that they're being followed, with Lucas telling them to meet him at Elm and Cherry. They run through houses and lawns as the soon intercept with Lucas, but with Brenner's men on their trail. A van then intercepts in front of them, driving up the road to stop them, but El causes the van to be hit by telekinetic force, flipping it upside down and giving them time to escape, while Brenner and his team are blocked. The quartet then arrive at the junkyard spot, with Lucas forgiving El as she forgives him as well, and then shaking Mike's hand finally.
Hopper and Joyce then arrive at the police department, with them being initially confused as they both demand for him to be let go, but they see the army supplies in his car which causes Hopper to be distrustful towards him, telling them that they won't believe him. Karen and her husband are then visited by Agent Frazer, disguised as a police officer, as they check through their stuff. Karen is then told that Mike had been hiding 011, but then is assured by Brenner himself as she unknowingly gives them their hideout location.
Lucas then lays out the building perspective, with them implying that the gate should be in there somewhere and that the building is government-sanctioned to build weapons to fight against the Cold War in 1983. Dustin then spots a helicopter in their direction, with the quartet hiding their bikes and then hiding in a nonfunctional bus. At the police department, Jonathan gives information and the picture of the monster, but Joyce is angry at him because of it as they then reconcile. Hopper, however, hears a very silly fight between Troy's mother and a deputy. He then learns from Troy about 011, basing it from mostly irrelevant and biased information.
Steve, on his car with a gnarly scar on his face, is then handed store-bought pills from Tommy. When he hears bad gossip about Nancy and Jonathan, he suddenly has a change of heart and confronts Carol and Tommy before he leaves in his car, from his now-toxic friends.
Hopper and Joyce then get Nancy and Jonathan to help find Mike, Dustin, and Lucas, as well as El. They then gather information about the monster and the kids, before they acquire a comm radio at Jonathan's home. Dustin, Mike, and Lucas discuss to one another if they are actually caught up with the bad guys or not, before Mike reluctantly answers. They then give them their current location.
Steve, with his now set of ways, goes to the theater where they defaced the sign and asks to help. The owner reluctantly allows him to help, not before realizing that he is one of the people who were convicted in the crime. Karen and her husband discuss trying to find Mike, despite Frazer's command to stay. Dustin, still in the bus with the other three, says that he doesn't have a good feeling, when they see two cars pull up with three agents, armed. They then hide and stay still, but one notices the bikes under the bus and slowly opens the door, to which he is knocked out by the Chief, who tells them to go.
Joyce, Jonathan, and Karen are at the Byers residence when Hopper returns with Lucas, Dustin, Mike, and El to the house. Mike then tells them the theory of the flea and the acrobat, at which point that he concludes about the gate, that it interferes with the Earth's electromagnetic field and compasses. Joyce and Nancy both ask Eleven to find Will and Barbara in the Upside-Down, but she can't find them, as the comm radio they are using is too small to track them. When all three of them ask how to find another way, she immediately sees the bathtub in the bathroom while in there, and tells them about the bath.
Dustin then calls Mr. Clarke to get information on sensory-deprivation tanks, and lists the materials they need from both him and El. Hopper and Jonathan get de-icing salt from Hawkins Middle School, Dustin and Lucas set up the kiddie pool that Joyce used for bobbing for apples, and Mike and Nancy get hoses from a nearby shed while Joyce duct tapes the visor on a set of goggles for Eleven. Mike fills up the pool with lukewarm water, Lucas sets the temperature for lukewarm, Jonathan and Hopper then dump the de-icing salt, and Duncan tests the density of the water with eggs. El is then placed in with the goggles, where the light flickers off as she astral projects again. She finds Barbara lying on the ground, as she slowly walks up to her. She finds her corpse, partially eaten, decaying, and with a slug-like creature in her mouth. Nancy asks if Barbara is OK, El yells, "Gone!" numerous times, scared. She finds Castle Byers in the Upside-Down as well, finding Will cold and frightened on the bed. She relays messages from Joyce to Will that they are going to find you and to hold on. Will then disappears from the astral region, to El's whimpering as she wakes up from the bath, crying and scared.
Hopper is then given information about Castle Byers from Joyce and Jonathan, and prepares to leave. Joyce, worried about Will and his welfare and state of being, goes along as well despite Hopper's warning. Jonathan, however, is told not to by Hopper as well as Joyce, but both him and Nancy decide to sneak out of the building to get the supplies from the station, from which he agrees. They go to the police station and steal the army supplies, as well as a fire extinguisher.
Hopper and Joyce cut the fence on the way in. They trespass in order to find the entrance but they are caught by security guards outside, as they surrender and are handcuffed. In the Upside Down, Will is singing to himself "Should I Stay or Should I Go?" quietly as he shivers in Castle Byers. The monster then growls, as Will sits upright, scared, as it approaches the fort. It then destroys it, carrying off Will to an unknown place.
In the Laboratory, Joyce is handcuffed to a chair parallel to another chair on a metal table, in an interrogation-like room. She screams to be let out, as Brenner arrives and interrogates Joyce as to the location of El and being in contact with Will, despite having tried to kill his friends and so. Joyce angrily refuses, due to the actions of capturing 011 for his own, faking Will's death, and leaving him in the Upside Down instead of reaching out to him. Hopper, however, is tasered repeatedly into leaking out his knowledge of the Laboratory, led by Agent Connie Frazer. He reveals that about the experiments, objectives, their killing of Benny Hammond - the restaurant owner who 011 went to, the faking of Will's death, and their scuffing up of tracks. He then negotiates a deal to let him and Joyce go, to get the supplies needed, and to find Will and to bury the hatchet soon after.
Meanwhile, at the gym, Dustin, Mike, Lucas, and El wait patiently in the gym with El wrapped in a towel. Mike then goes out the door to look for Nancy and Jonathan, finding Jonathan's car gone. He then tells the trio, in which El reveals that they are going to fight the monster. At the Byers' residence, Nancy and Jonathan extensively set up a crude trap layout, laying down gasoline, bear traps, and a yo-yo to indicate the monster is trapped. Nancy loads the revolver, and Jonathan hammers long nails into a baseball bat.
Brenner then arrives at the room where Hopper is being held in, offering a cigarette and a lighter, which Hopper takes. He then asks for Brenner's word that they will remain neutral and to not target Mike, Dustin, and Lucas, which Brenner accepts. Hopper then reveals the deal to Joyce, in which both put on hazmat suits for protection against the Upside Down's atmosphere, grab flashlights, and enter the Upside Down. Brenner, in actuality betraying Hopper due to the high possibility that they will die, goes armed and rides toward Hawkins Middle School.
Now in the Upside Down, Hopper tells Joyce to breath deeply in and out. During this, he remembers seeing Sarah, by playing with her in the park happily with his wife along. She then breathes heavily, in which a frightened wife watches while Hopper tells her to breathe in and out. He then snaps out and asks Joyce if she is OK, to which she says, "Yeah." Back at the house, Jonathan and Nancy cut their hands with kitchen knives to attract the monster, with both reviewing the plan: straight into Will's room, and to not move until the monster steps in the trap, at which Jonathan will immolate it with a lighter.
At the gym, Mike wonders what will happen, at which Lucas and Dustin agree to stay in the gym to protect El. Dustin then goes to the cafeteria kitchen to find chocolate pudding, accusing the lunch lady of actually hoarding it for herself, to the rest of the group's worries.
Nancy and Jonathan, with their hands bandaged, comfort each other while they wait for the monster to arrive. Unexpectedly, Steve knocks at the door, which Nancy opens then tries to close him out by telling him that there is danger, but he enters forcibly after seeing Nancy's bandaged hand. Confused by the traps set up, Jonathan tells him to leave but Nancy grabs the revolver and aims it at Steve ordering him to get out. Just then, the Christmas lights blink, as the monster arrives through the ceiling wallpaper, scaring Steve out of his mind. Barricading themselves into Will's room, Jonathan holds the lighter while the monster passes. However, the electricity jolts stably, with the monster nowhere to be found.
Hopper and Joyce, now in the Upside Down version of the Hawkins forest, find a broken egg. They then come across Castle Byers, now destroyed by the monster. Looking at a stuffed tiger, he hearkens back to when Sarah, now in the hospital bald - cancer, was reading alongside with Hopper a book with the same exact stuffed tiger, then shown crying on a stairway. Hearing Joyce's voice, he snaps out of the memory.
At the Byers house, the trio looks for the monster. Steve, frightened, tries to call someone but Nancy grabs the phone out of his hand and says that the monster will return, and to leave now. He then bolts out the front door, fumbling his keys in order to get in the car, but sees the lights pulsating. He then looks at it sternly. In the living room, the lights go out before the monster pins Jonathan down. Just then, Nancy shoots the monster to no effect, but it directs its attention to Nancy. It then stomps toward her, but Steve interferes, grabbing the baseball bat and knocking and hitting it to the bear trap. Jonathan then lights the trail of gasoline, lighting the monster on fire. In the Upside Down, Hopper and Joyce hear the monster's screams and follow it. Jonathan then extinguishes the fire, but finding the monster not there again, believing it to be dead. In the real world, the Christmas lights pinpoint the location of Joyce and Hopper, as Jonathan realizes. He calls out to Joyce, and she calls back, being able to hear him. She then leaves. The trio then walk outside and see a streetlight blinking. Nancy, relating it to the monster, asks where its going. Jonathan replies that its not the monster.
Dustin and Lucas find the cached pudding for El, confirming that lunch lady was hoarding it for herself. During their alone time, Mike and El contemplate on having her as an adoptive family member. Mike says that she will be well-fed and cared after, and can live with him after. With El asking to not lie, Mike then says that they could go to the Snow Ball, a dance at the middle school for winter, and that you go with someone that you like more than a friend. Explaining this, he then kisses her for two seconds then pulls back; both are amazed. Mike then goes outside, believing that its Nancy and Jonathan, but he sees the agents parking in the school and looking for them. He tells the rest of the group, and they escape.
While in the school hallway, Frazer's group of agents surround them. El, protecting the rest, proceeds to use telekinesis to squish their brains, as they bleed from their eyes, into a pulp. She then stops, which kills all of them, but weakens her immensely. She collapses to the ground, unconscious. The group tries to wake her up.
Hopper and Joyce then walk through the Upside Down's Hawkins. As they walk through, they find a building with massive amounts of black roots: the monster's nest. They go inside, aware of the surroundings.
Still trying to wake her up, Brenner encounters them and has the agents restrain Dustin, Lucas, and Mike. He then sits near El and picks her up, being unable to move but talk. He then tells her that he can take her home to the Laboratory, where they can make her better and that no casualties happen. El, realizing the usage of her and the agents, finds him bad. Just then, Mike notices a large amount of blood on the floor from Frazer's agents, realizing that it can detect blood, as it enters through the wall. The agents them let go off the trio, as they take El to a classroom. Leaving the agents behind, the monster then jumps on top of Brenner, killing him and the agents.
In the Upside Down, Hopper and Joyce find the nest and look through it to find Will. While searching through the bodies, they find some eaten and some alive but drained of life. Joyce, looking for Will, finds him with a large, alive tube in his throat. Joyce and Hopper takes out the slug-like creature, with him shooting it with his gun.
Dustin, MIke, and Lucas, now in a classroom, take El to a desk where she can heal. Mike consoles her by reminding her of the life she can have once it is all over, as she asks, "Promise?" Mike promises. Just then, the monster kills the rest of the agents, and breaks into the classroom. Lucas arms himself with a slingshot, shooting projectiles at it to no effect. The fourth time he shoots, however, seemingly knocks it to the chalkboard. They then see El walking toward it, being the one restraining it there. Mike asks her to stop, but she pushes him back with telekinesis. Ignoring her ongoing nosebleed, she says, "Goodbye, Mike" as she proceeds to seemingly kill the monster, causing an amount of force that transforms it into small particles and it disappears. Along with El. The electricity then jolts back. Mike then yells for El, with others yelling for her as well, but she doesn't appear.
Putting Will on the ground, Hopper asks Joyce to lift his chin, pinch his nostrils and breathe into his mouth twice at his command, while he does chest compression, performing CPR together. During this, Hopper remembers being in Sarah's hospital room, seeing doctors perform CPR on her as the EKG monitor flatlines, him embracing his wife, distraught. Hopper then repeatedly punches Will's chest. This causes him to wake up, with Joyce encouraging him to breathe in and out, with Hopper putting on an oxygen mask for Will, as Joyce tearfully hugs him. Karen and her husband then find Mike, as Karen embraces him.
In the hospital, Will is sleeping until he wakes up and sees Jonathan and Joyce. He asks where he is, Jonathan tells him that he is safe now. Consoling him, Jonathan and Joyce catch up a little bit with him, and bring him some supplies, such as a mixtape. In the waiting room, Mike waits while Lucas and Dustin sleep when Jonathan signals him to go. He wakes up Dustin and Lucas, as they tenderly embrace him. They tell him the whole history of what happened since he went missing, including 011. Nancy then leaves, as Jonathan looks back then forward. Hopper then leaves smoking a cigarette, but not before entering a car with men in black suits, as they drive away.
One month later, on Christmas Eve, Will plays Dungeons & Dragons with the duo. He then comes across a Thessalhydra, but rolls a 14 and successfully casts a Fireball, with painfully kills the Thessalhydra. They cheer and celebrate the action, but quickly quarrel when the campaign is over, which takes 10 hours but presents a lot of plot holes. Jonathan then comes to take Will home, and he does, saying goodbye to his friends. Nancy, before Jonathan's exit, gives him a gift before he leaves and kisses him on the cheek. Will then opens it to reveal a new camera for Jonathan, as they drive home. Nancy then cuddles with Steve, who asks if she gave it to him, implying that Steve bought the camera as a "sorry" gift. She says yes.
At the police station, a Christmas party is there, as Hopper arrives to grab Eggos waffles out of the refrigerator, to which two deputies exclaim it, as the assistant Flo puts out his cigarette and says Merry Christmas to him, to which he replies the same. He then leaves the station, driving to an unlocked safe box and putting the waffles on a plate inside, closing it. It is a remembrance gift for 011, since she is either presumed dead or in an unknown place. Hopper then leaves.
Jonathan and Will then arrive at home, with Joyce making Christmas dinner. Jonathan takes pictures with his new camera, "documenting" the pictures. Will says, after observing the wrapped gift offscreen, that it is an Atari console because of Dustin's being the exact weight. Joyce then says that we shall see. Will then excuses himself to wash his hands in the bathroom.
In the bathroom, though, he feels sick and coughs up a small slug-like creature in his throat that goes down the sink. He then looks wearily into the bathroom mirror, turning on the faucet as the room all around him then starts to look as the Upside Down for a minute, before switching to reality. He looks in the bathroom mirror and turns the faucet off, slowly. There is then a small growling heard.
At the dinner table, Will returns very weirdly into his chair. Joyce asks if he is OK, to which he responds, "Yeah, I'm OK." The family then commences dinner, as they talk about Dungeons & Dragons as the camera pulls back into a wide angle from a house window, as it snows outside. The TV logo then shows itself one last time as it fades.