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Stranger Things Wiki

"Chapter Four: The Sauna Test" is the fourth episode of the third season of Stranger Things and the twenty-first episode overall. It premiered on July 4, 2019.


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.


Monday, July 1, 1985

El is lying in bed with Max, worrying over Heather and Billy. Max convinces El to calm down marginally, and then they read comic books. At the same time, Mrs. Driscoll has been restrained by police and is being taken out of her home on a stretcher. With fertilizer all over her face, she hysterically screams "I have to go back!" repeatedly as she is placed in an ambulance and rushed to the hospital. While this happens, Tom and Janet Holloway wake up, bound, inside Brimborn Steel Works. Their daughter Heather approaches and takes off Tom’s gag, and Tom pleads to Heather that "you don’t have to do this, you can stop this". Heather responds that "there is no stopping it", before she and Billy depart. The Mind Flayer then arrives and launches one vine apiece onto the couple’s faces, each one pulsating, implanting them and turning them into the Flayed.

Tuesday, July 2, 1985

Hopper wakes up from his injuries from the night before, retching and then getting up only to find that he didn’t have any clothes on, much to Joyce’s consternation, having been taking care of him. They try to identify who attacked Hopper, and Joyce notes that they didn’t drive a car, which Hopper picks up on.

In the Hargrove house, Lucas tries to reach Max via radio, but she tells him to shut up and turns off her radio. Mike then calls, and tells her that there’s a serious situation and to come to his house immediately. There, the rest of the Party tries unsuccessfully to reach Dustin. Dustin however, is with Steve and Robin scoping out the Russians’ base of operations, trying to get inside. Steve suggests sneaking and taking out the armed guard for his pass key, but then him and Dustin get to arguing before Robin rushes off on her own plan, telling them to stay put.

At The Hawkins Post, Tom Holloway, the lead journalist, angrily interrogates Nancy and Jonathan for following up on the rat lead as he had ordered Nancy not to. He berates them for trespassing on her home, for taking a "paranoid schizophrenic" seriously, and for falsely identifying themselves as reporters. Due to the threat of lawsuit, he fires them both.

Will explains the Mind Flayer’s return to Max, Lucas, Mike, and El

Back at Wheeler house, Will explains how he has been sensing the Mind Flayer. El objects that she closed the Gate to the Upside Down, but Will indicates that the piece of the Mind Flayer that was within him may not have returned to the Upside Down. They determine that he must have sought out a new host.

Arriving at city hall, Hopper asks Mayor Kline if he saw the man who attacked him, having seen him go into Kline’s office a few days ago. Kline claims not to remember, trying to convince Hopper that he was only a maintenance plumber, but Hopper responds with his knowledge of Larry passed out on coke and cheating on his wife in the past, as a threat. Larry fires back with his own threats and knowledge of Hopper’s, saying that "one call to Tom at the Post and you’re done, buddy". Larry goes to escort Hopper out, but Hopper then assaults him, demanding the information, and although Larry’s secretary tries to call the police, Joyce unplugs her phone. With Larry uncooperative, Hopper repeatedly threatens to cut off Larry’s finger, and Larry eventually admits that he was bribed by that person (who works for Starcourt Mall) in order to help them expand into East Hawkins. Hopper demands to see records of the purchases, and takes Larry hostage to find them.

On the way home, Nancy shares her suspicions with Jonathan that there was something fishy about their firing, but Jonathan chuckles, saying that she always manages to convince herself that she’s in the right, that she is living in a bubble because she doesn’t have to deal with college payments or mortgages. Nancy fires back that he doesn’t understand how humiliating her internship job was, but Jonathan maintains that she doesn’t understand, so she acknowledges that they simply don’t get each other anymore, and she returns home crying.

Returning to Scoops Ahoy, Robin reveals that she bought Starcourt Mall blueprints and that air ducts lead to the restricted rooms they’re trying to get into, and so they try to shove Dustin inside but are unable to do so. At the Hawkins Community Pool, the Party is spying on Billy, who is oddly wearing a shirt in the open sun because the Mind Flayer likes it cold and dark. Max is confused because Billy looks normal, so Will explains that the Mind Flayer is trying to "hide", that Billy is "dormant" until the Mind Flayer needs him. Mike then forms a plan to get Billy into the sauna in order to force the Mind Flayer to react to the heat.

Hopper talking to Larry Kline in his mansion

Again at Scoops Ahoy, Erica is recruited to go into the air ducts in exchange for a smorgasbord of ice cream and free ice cream for life. Meanwhile, Hopper and Joyce arrive with Larry Kline at his mansion, going to grab the land deeds from a safe within Larry’s bedroom; not for blackmail, but for protection, due to how "scary" his bribers are. Joyce and Hopper figure out that there is likely a powerful machine on one of the properties, and Hopper prevents Larry from escaping out the window.

Nancy confides in her mom at the Wheeler house, and Karen tells Nancy that she’s proud of her for standing up for herself, that she should finish her story. At the pool however, the Party are preparing to trap Billy. Mike tries to apologize to El, but El surprisingly says that Hopper might be right, that they were spending too much time together and that she didn’t get to see the world. Max meanwhile, desperately hopes that Billy isn’t a host for the Mind Flayer.

Erica moving through the Starcourt Mall air ducts

Winnie Kline, Larry’s wife, arrives at his mansion to find him handcuffed to his bed. He demands a phone to get vengeance against Hopper, while Hopper himself is out with Joyce investigating the properties from earlier. Concurrently at the Starcourt Mall, Erica makes her way through the air ducts to open the loading bay doors from the other side, allowing Robin, Dustin, and Steve inside.

Will, Mike, El, Max, and Lucas trapping Billy in the sauna

Once more at the pool, Mike lures Billy into the sauna, and El locks him inside. Billy calls out to Max, but she orders the Party to turn up the heat anyway. Nancy on the other hand arrives at the hospital to see Mrs. Driscoll, lying that she is "Nancy Driscoll" so that she can visit her, looking through her records. At the mall, Steve opens up one of the Chinese shipment boxes only to find some form of radioactive material inside. The room begins to shake, so Dustin and Steve frantically press buttons in order to reopen the doors and leave, but they accidentally activate an elevator of sorts that sends the room plummeting into the earth. Again in Mrs. Driscoll’s hospital room, Nancy is furiously taking notes while Driscoll’s heart rate continues to increase.

At the pool, Billy begins to break down sobbing, saying to Max that "he made me do it", describing "he" as a "giant shadow", the Mind Flayer. Continually sobbing, Billy says he tried to stop it, that it isn’t his fault, but Will senses the Mind Flayer at work, realizing that Billy is "activated". Mike orders Max to get away from the door, just in time for Billy to smash through the sauna window where her head was. Billy tries to unlatch the door, but Lucas hits him in the face with a slingshot, sending him back into the sauna where he begins convulsing as the lights flicker.

In both Mrs. Driscoll’s hospital room and the pool, lights continue flickering as both Mrs. Driscoll and Billy become enveloped in black veins. They both scream, and Billy begins attacking the door, slowly breaking it down. Billy eventually smashes through, and although El uses telekinesis to restrain him, he breaks free and begins to choke her until Mike hits him in the back of the head with weight equipment, saving her. Billy then goes to attack Mike until El levitates Billy up with telekinesis, and throws him completely through the concrete wall of the pool house. Mike comforts the wounded El, and Billy staggers away.

At the Brimborn Steel Works, Heather tends to Billy. Billy says El could have killed him, which Heather responds; "yes, but not us", as the entire basement full of hosts comes into view.




  • "We'll Meet Again" by Vera Lynn - El, Mike, Lucas, Will and Max watch Billy run away after the Sauna Test.

Original score

  • "Happy Screams" - Eleven shares her continued worries about the state of Billy and Heather with Max.
  • "Lights Out" - The monster approaches Heather’s parents.
  • "Tendril" - Heather’s parents become flayed.
  • "The Ceiling is Beautiful" - Hopper wakes up in the cabin.
  • "Code Red" - Mike, Lucas and Will attempt to gather the other members of the party to them.
  • "Looking for a Way Out" - Robin takes money from the tip jar and leaves to find a way into the loading room.
  • "Six Facts" - Tom yells at Nancy and Jonathan before firing them.
  • "We Don't Understand Each Other" - Nancy and Jonathan argue in the car.
  • "Blueprints" - Robin, Dustin, and Steve form a plan using the blueprints Robin had acquired.
  • "Leap of Faith" - Mike forms a plan to lure Billy into the sauna.
  • "Land Deeds" - Mayor Kline retrieves the land deeds from his safe in his mansion.
  • "Theoretically" - Joyce explains to Hopper the machine responsible for disturbing the electromagnetic field must be located at one of the properties Mayor Kline has deeds to.
  • "You're a Fighter" - Karen consoles Nancy.
  • "A Familiar Shape" - The kids taunt Billy in order to lure him to the sauna.
  • "Turn On The Lights" - Billy finds who he thinks is taunting him.
  • "Making Contact" - Billy enters the sauna.
  • "They Found Us" - The kids lock Billy in the sauna.
  • "Possessed" - Nancy sneaks in to Doris Driscoll’s hospital room.
  • "Not Chinese Food" - Steve opens a box and finds a mysterious green tube before the room/elevator they’re in rapidly descends.
  • "Mirkwood" - The Mind Flayer activates Billy, which leads to him breaking out of the sauna. Doris Driscoll begins to scream. Eleven tries to fight Billy off.
  • "Sauna Test" - Eleven sums up the little strength she has left by throwing Billy through a brick wall, saving Mike’s life in the process.
  • "I Can Save Them" - Eleven collapses in Mike’s arms as Billy makes a run for it.

Behind the scenes

The Sauna Sequence

Director of the episode, Shawn Levy revealed that the sauna sequence between Billy (Dacre Montgomery) and the kids required at least three months of story-boarding and stunt choreography before the team started shooting it. He explained that they spent entirely four days, 10-12 hrs everyday, in the set working out the scenes. He also had to film the entire sequence with Millie, Dacre, Finn, Noah, Caleb and Sadie using only two handheld cameras for maximum intensity. While commending Millie Bobby Brown and Dacre Montgomery for their sublime performances, Levy also revealed that when Eleven (Millie Bobby Brown) collapsed into Mike's (Finn Wolfhard) arms at the end of the sequence, it was due to real exhaustion of the actress.[1]

Shawn Levy and Dacre Montgomery, during a read-up of the sequence.

The only scene where a stunt double was required was when Billy was pinned to the wall with a barbell to get a wider view. Excluding the scene, the whole fight sequence was filmed with Millie and Dacre. Levy also mentioned that the moment when Billy was getting possessed by the Mind Flayer, it was Dacre Montgomery’s idea to have Billy’s feet dragging on the floor, which he shot a full on close-up.[1]

Since the sequence had no dialogue, Levy played out some original scores from the first and second seasons of Stranger Things, so that the actors could get in the mood of the horrific sequence.[1]



  • On December 9, 2018, a teaser trailer for the third season was published across social media, listing the titles of the eight episodes, the fourth of which was "The Sauna Test".
  • This is the first episode where Erica joined Dustin's team.
  • Billy dropped the F bomb in this episode.
  • This is the only episode in season 3 where Grigori does not appear