The boys bring Eleven to Mike's house, where she sleeps in the basement. Lucas and Dustin are hesitant to involve themselves with Eleven, finding her strange and a distraction from finding Will, but Mike convinces them he will arrange for Eleven to approach his mother so that she can contact the authorities.
The next day, Mike nicknames her "El". She refuses to meet Mike's parents, warning Mike that involving anyone else risks attracting the attention of dangerous people. Scientists from the laboratory find a substance oozing from the walls of Joyce's home. At Mike's home, Eleven recognizes and points out Will in a photo before turning the boys' D&D gameboard upside down to indicate to them that is where he is.
As the community searches for Will, under the coordination of Hopper and the local police, Mr. Clarke, the boys' science teacher, discovers a scrap of a hospital gown outside the laboratory grounds. Hopper, meanwhile, is also tasked with investigating Benny's rather suspicious "suicide". Hearing from witnesses that a child in a gown was stealing food from the dinner yesterday, Hopper suspects that it might be connected to Will's disappearance and decides to take a closer look at the laboratory.
Under pretext of going to an assembly regarding Will's disappearance, Nancy goes with Barbara to a party at Steve's house.
Jonathan goes on a short trip out of town to visit his and Will's deadbeat father, Lonnie, but learns nothing from him about Will's whereabouts. An unhappy Jonathan returns to Hawkins that evening and goes into the woods with his camera to take some pictures of nature where he finds Steve, Nancy, and their friends roughhousing around Steve's swimming pool, shotgunning beer cans. Nancy successfully downs her can, but when Bard is peer-pressured into doing the same, she accidentally cuts herself trying to pierce the can. Uncomfortable with her peers' drunken antics, Barbara remains alone by the swimming pool as they go inside, a drop of blood from her cut falling into the water. Jonathan sees her and takes a picture of her, but when he looks away to change his film, Barb hears the flickering of the pool's electrical outdoor lights behind her and a soft growling, turning around just as an otherworldly monster lunges at her. Jonathan looks up from his camera, the pool's diving board is empty, with no trace of Barb or the monster anywhere.
Joyce receives another call from Will, hears music from his room, and sees something coming through the wall.
This episode provides examples of:
- Armor-Piercing Question: Joyce to Hopper when he expresses doubt that she really received a phone call from Will.Joyce: You think I don't know my own son's breathing? Wouldn't you know your own daughter's?
- Bait-and-Switch: Jonathan hears a womanly shriek in the woods and runs towards it as the show's music crescendos and gets more frantic to emphasize the urgency of the situation. When the music is as fast as it can be, the womanly shrieks turn to laughter and we see Jonathan was running towards Tommy and Carol getting wasted at Steve's house instead of The Reveal of a new clue relevant to the plot.
- Big "NO!": Joyce after Will calls again and the second phone goes kaput.
- Can-Crushing Cranium: Tommy smashes a beer can against his head at Steve's get-together.
- Dude, Not Funny!: Hopper calls out Powell for making fun of Joyce's Sanity Slippage when her son is missing. Steve also tells Tommy to shut up when he jokes that Jonathan killed Will.
- Dumbass Has a Point: Played with; Callaghan hasn't exactly impressed with his policework skills so far, but when Hopper begins searching for Will from Benny's Diner on the presumption that he was the child seen there previously (actually Eleven, unknown to the other characters), he raises the actually pertinent question of why Will would suddenly appear at Benny's with a buzzcut stealing food. However, Hopper has by this point got his teeth into the theory and so brushes him off.
- Establishing Character Moment: While throughout the series so far we've seen Nancy primarily be concerned with her status at school and the prospect of dating Steve Harrington, her fundamental kindness and decency is established when, alone of the teenagers who encounter him putting up missing posters, she goes to say some words of comfort to Jonathan over his brother.
- Fanservice: Nancy takes off her shirt and spends the last minutes of the episode in her bra, making out with Steve all the while.
- Feet-First Introduction: The men in white hazmat suits, amongst them Brenner, are first introduced with a shot of their gumboots exiting one of their vans.
- Flashback Echo: When Mike hides El in the closet, she gets scared and flashes back to a memory at the facility where she was put in the Punishment Box.
- Flies Equals Evil: When Hopper arrives at Benny's diner, the sound of flies can be heard which immediately cues the audience into what's gonna come.
- Foreshadowing:
- When Steve, Tommy and Carol are inviting Nancy and Barbara to their party at Steve's house, they happen to see Jonathan putting up "missing" posters for his brother in the school corridors. When Tommy and Carol make snide comments about him, Steve chides them to knock it off. It's not exactly a passionate defence of Jonathan (and could easily be interpreted as Steve trying to stay in Nancy's good books), but it won't be the last time Steve unexpectedly goes against his friends when it comes to the subject of Jonathan Byers.
- The Demogorgon is never seen actually attacking Barb. Barb being dragged back into the pool is also uncharacteristic of the beast, which normally just pounces on and violently tears apart its victims. In season 4, it's hinted that the Demogorgan wasn’t the one who actually killed Barb.
- Funny Background Event: After Dustin and Lucas do a Spit Shake, Dustin in the background gives Lucas a "What the hell?" look and wipes his hand off on his shirt.
- Jerk with a Heart of Gold:
- Sheriff Hopper starts showing signs of this when he starts defending Joyce against Powell's insults.
- Steve also reveals some unexpected depths when he chides Tommy and Carol for making fun of Jonathan when they see him putting up "missing" posters for his brother, albeit in a less-than full-throated fashion.
- Kick the Dog: Dr. Brenner and his cronies establish early on that they are not a benevolent government agency when they kill Benny (the diner owner who takes good care of Eleven) after he's already convinced that the social services are there to routinely take some stray girl from him.
- Lady Looks Like a Dude: Both Benny and his patrons initially mistook Eleven for a boy. While Benny later realized his mistake, his sudden death leaves the other witnesses to report seeing an unknown "boy", causing confusion with the missing Will.
- Literary Allusion Title: To "The Monsters Are Due on Maple Street" and/or A Nightmare on Elm Street.
- Little "No": Eleven, when she telekinetically slams the door shut as Lucas tries to leave. Also earlier when she rejects Mike's plan to ring the bell at the front door.
- Mood Whiplash: Jonathan is looking for more evidence of Will near the barrier where he was taken when he hears a girl screaming. He rushes to the source, only to find that it came from Carol, who was being messed with by Tommy at Steve's get-together.
- Never Give the Captain a Straight Answer: Hopper is called to Benny's diner. Instead of informing him about the nature of the investigation, the operator just says "I think you need to get there right away".
- Never Suicide: Benny the diner owner is murdered by government spooks and made to look like he shot himself. Hopper doesn't buy it, because he knew Benny well.
- No Good Deed Goes Unpunished: Barbara, who agrees to party with Steve and his friends to make sure Nancy doesn't get too drunk and gets dragged into the Upside-Down.
- "No. Just… No" Reaction: Lucas' reaction when Mike tries to sell him the plan to keep Eleven hidden from the adults.
- No Social Skills: As is to be expected, Eleven doesn't exactly have the best understanding of appropriate social mores... as demonstrated to the horror and embarrassment of the boys when, after they offer her some clean clothes in place of her ragged t-shirt, she prepares to strip off in front of them.
- Nothing Exciting Ever Happens Here: According to Hopper, the worst thing that had happened in his four years of working in Hawkins was when an owl attacked Eleanor Gillespie's head because it thought her hair was a nest. Also, the last time when somebody was missing was in Summer 1923 and the last time that somebody committed suicide was in October 1961.
- No, You: Nancy calls Steve a cliché, and he retorts that she's the cliché with her grades and band practice.
- Parents Know Their Children: Joyce claims she knew it was Will's breathing on the phone because of this trope. She then questions Hopper if he wouldn't recognize his daughter's.
- Playing Sick: Mike has to pretend to not feel well when his mom catches him home after he was supposed to go to school.
- Please Put Some Clothes On: Played with, since she is already wearing clothes, but the boys are quite shocked and embarrassed when Eleven is about to take off her wet clothes right in front of them.
- Right for the Wrong Reasons: When a thread of clothing is found on the narrow drainpipe leading in and out of Hawkins National Laboratory, Hopper accurately reasons that a scared child might indeed risk crawling through it if they were running from something, as indeed one did. Unfortunately, Hopper is looking at it from the wrong direction; he is assuming that Will crawled through the pipe into the laboratory grounds, when in fact it was Eleven crawling out.
- Rule of Pool: There's a pool party with people dressed, so no surprise that people wind up in the pool.
- Sex Signals Death: Inverted. Barb dies because she's all on her own when everyone else is distracted getting laid. Nancy even seems to pick up on this, since after her encounter with the Demogorgon she lets Jonathan stay in her room for the night (with the lights on and a loaded gun within arm's reach) even though they don't have sex.
- Soft Water: Deputy Callahan brings it up when retelling a story from a local who claims to have taken a dive into the water at the bottom of the quarry from the top of the cliff on a bet. Chief Hopper immediately calls bullshit, informing Callahan that from that height, he would've broken every single bone in his body upon hitting the water. This is a handy factoid when Will's "body" is found in it – intact.Hopper: You make that jump from this height, that water turns into cement. Hits you like a ton of bricks. Break every damn bone in your body.
- Soundtrack Dissonance: "Should I Stay Or Should I Go" is used to this effect when Joyce finds it blaring from Jonathan's room shortly before the lights go out and the monster appears.
- Spit Shake: Lucas and an unwilling Dustin demonstrate this to Eleven to teach her the meaning of an unbreakable promise.
- Spit Take: While The Party and The Wheeler Family are enjoying dinner, Mike notices Eleven coming down the stairs out of sight of his family, cue a startled spit take as he chokes on his glass of milk. Dustin prevents her from being noticed with a 'spasm' however.
- Suspiciously Apropos Music: When Joyce has run from the monster in her house, she is drawn back in by a signal from Will... in the form of the song "Should I Stay Or Should I Go?".
- Sweeping the Table: El dramatically sweeps the figures from the playboard before turning it around and using it as a Phlebotinum Analogy for the Upside Down.
- Unwitting Instigator of Doom: Nancy convinces Barb to come along with her to Steve's pool party and even attempt to try to shotgun a beer can to join in the fun. This results in her hand getting accidentally sliced open, and when Barb is awkwardly sitting outside at the pool when the rest of the teenagers head inside, a drop of blood in the water draws the monster to her, resulting in it kidnapping her like Will before anybody can notice.
- You Must Be Cold: Implied to have happened off-screen. When the boys encounter Eleven at the end of the previous episode, she is only wearing the t-shirt she got from Benny. At the beginning of this episode, she is seated in Mike's basement wearing his jacket, and Mike himself is looking soaked, implying he gave it to her.
