Joyce, Hopper and Murray drive to the mall as quickly as possible. At the food court, Eleven is in agony as something wriggles beneath her skin. It LOOKS painful. Jonathan of all people gets an idea. He runs to one of the restaurants, grabs a knife and heats it up using the stove. He returns with a wooden spoon for El to bite down on as he cuts into her leg; we see blood and puss, but that's not the worst part. No, the worst part is him sticking his fingers in to try and remove whatever is in her leg (don't worry, he has gloves on). The other characters actually wince. El screams for him to stop and uses her powers to draw the creature out of her leg. She throws it several yards and Hopper steps on it. Cue credits.
The Party catch Joyce, Hopper and Murray up to speed on what's going on. They go over the blueprints of the underground facility. Dustin offers to navigate for Hopper, Hopper only agrees to do so over the walkie-talkies. However, for the walkie-talkies to reach them, Dustin informs them he needs to be next to his radio tower, so the signal is strong enough. Steve and Robin drive Dustin and Erica to the top of the hill Dustin calls "Weathertop." Joyce, Hopper and Murray will assault the facility, while the party will leave, having done more than enough already. Hopper and Eleven have a father/daughter heart-to-heart. Hopper tells Mike to "be careful," seemingly as a peace offering.
The party hops into the Station Wagon, but it won't start. Jonathan pops the hood and realizes the ignition cable is gone. Which is, of course, when Billy starts revving his vehicle. The party races back into the mall.
In the Elevator, the adults go over the plan one last time. The doors open, and they come face to face with Russian guards holding them at gunpoint. Hopper shoots all four of the guards and they each grab a uniform.
The Scoops Troop drives off-road and makes it part way up the hill. They get out and walk up the rest of the way. Mike is on the walkie-talkie trying to reach them to let them know Billy has found them. Nancy takes a gun off of one of the dead security guards. They notice the car that Eleven threw earlier and realize if they can get the ignition cable they can leave. They try to push it over but can't. El tries, but ultimately proves too drained to move it.
Dressed as guards, Murray manages to bluff their way past the guard and into the facility. Murray, using the call sign bald eagle (clearly given to him by Dustin), contacts Scoops Troop on the hill and crawls into the air vents.
At the food court, the gang manages to flip the car over using physics. Mike seems to be the one who came up with the plan. Eleven finds a can of new coke in the trash and tries to crush it with her mind (like in season 1), she can't. For the moment, her powers seem to be gone. As Jonathan looks for the ignition cable, Mike feels the presence of the Mind Flayer. Max and Mike see the creature above them on the glass roof. The gangs runs before it can break in. It does, lands in the food court and roars.
Russian Terminator and company arrive underneath the mall, only to find the dead men left by Hopper. Joyce and Hopper are bickering again, and Joyce does an impression of Hopper that had me in stitches. I love Winona Ryder. Even funnier is that the Soviet uniform she's wearing is way too big for her. Hopper says he thinks they make a pretty good team. They plan on a date, and Joyce says she might stay if this thing works. Which is the point where we know at least one of them is screwed, probably Hopper.
Murray crawls through the vents, reaches an intersection and calls the Scoops Troop for directions. They tell him to go right. On the top of the hill, they notice something is going very wrong at the mall. Dustin tries to make contact, referring to them as "Griswold Family." The Monster destroys the walkie-talkie Dustin's voice is coming out of. The "Griswold Family" is hiding in a manner reminiscent of Jurassic Park. Will, Jonathan, Joyce and Lucas are behind the car, and it brings to mind the scene in the kitchen where Tim and Lexie are hiding from the raptors. A scene I first saw when I was about 7, and to this day gives me the chills. Max, Eleven and Mike are hiding underneath a desk similar how the Hobbits hide from the Nazgul in The Fellowship of the Ring.
Steve, being Steve, can't sit by while the others are in trouble and runs to the car to get them the hell out of there. Dustin contacts the adults to inform them "we have a problem."
While the Monster has its head turned, Max, Mike and El try to escape through the Gap store. Unfortunately, they have to run over broken glass, making noise and El knocks something over, grabbing the monster's attention. It sends its tendrils into the store, searching for the kids.
Murray arrives at the power generator and starts pulling wires, screwing with the machine, the alarm begins to sound.
Just as the monster is about to find the kids in the Gap, Lucas fires his wrist rocket at a balloon, distracting the monster long enough for everyone to escape out the back.
Hopper and Joyce arrive at the safe holding the keys, only to find that the code Murray gave them doesn't work. Dustin hears them arguing about it over the walkie-talkies. He doesn't know Planck's constant by heart, but he knows someone who does.
The Party arrives at the car and tries to start it, even with the ignition key it won't work. Billy speeds towards them and Nancy shoots, none hit Billy. Just as Billy is about to hit her, Steve slams into him, saving the group, because Steve is a fucking boss. Up on the roof, the monster appears, and Steve and Robin see it for the first time. Jonathan has gotten the Station Wagon working and the gang takes off after picking up Steve and Robin. The monster chases them. What comes next is one of the most unexpected things in the entire season.
In what might be the ultimate brick joke, we cut to a white house and the words: Salt Lake City, Utah appear on-screen. A teenage girl is reading A Wizard of Earthsea by Ursula K. LeGuin (a great book by the way) when Dustin's voice comes over the radio. Its Suzie, Dustin's girlfriend, he was telling the truth the whole time. She answers, it's so sweet that it's almost disgusting. He gets her to change frequencies to whichever one Hopper is using. He asks her for Planck's constant, but Suzie is a little annoyed that she hasn't heard from him in a week, and that he doesn't know Planck's constant. She only agrees to do it if Dustin sings her the theme to The Neverending Story. I swear I'm not making this up. Dustin reluctantly complies. The looks on the faces of everyone who can hear it over the Walkies is absolutely priceless. Hopper in particular. But she gives up the number and it opens the door.
Billy emerges from his car, just as Mike, Max and Eleven emerge from the mall. Separated from the others and moving slowly because of Eleven's injury, they catch sight of Billy and run back into the mall. Billy goes after them, calling the monster back to him. The group in the car turn around and race back towards the mall.
Underneath the mall the generator is going nuts. Joyce and Hopper enter the control room and Hopper intimidates the scientists into leaving by firing his AK into the ceiling.
Billy attacks Max, Mike and El, knocking Max and Mike out with little effort. To his credit, Mike does immediately put himself between Billy and El, trying to stop Billy, but Billy easily overpowers him. Billy then knocks out El and carries her off.
Joyce and Hopper enter the keys and are about to turn them when Russian Terminator arrives and begins to fight Hopper.
Billy takes El back to the food court where he offers her up to the Mind Flayer monster made of human goo. The creature opens its maw, showing its teeth. Its prehensile tongue comes out. Suddenly, an explosion hits the creature from above. The gang from the station wagon are on the second floor and throwing fireworks at the creature (go Lucas) before it can hurt El.