The Stranger Things play totally unlocks Stranger Things Season 5, Vol. 2

The following contains spoilers for Stranger Things Season 5, Volume 2.

Watching Stranger Things: The First Shadow on Broadway after watching Stranger Things Season 5, Volume 1 was a surreal experience.

Not only were audience members treated to the play's spectacular special effects — seriously, you'll feel like you're in an episode of Stranger Things — but we also got to see how the play linked to Season 5.

Mentions of Henry Creel's (Jamie Campbell Bower) childhood in Nevada made audience members gasp as they recalled the mysterious Nevada cave system in Henry's mindscape. Elsewhere, young Joyce's production of Oklahoma! in The First Shadow tied to Henry's memories of his time at Hawkins High, through which Max navigates in Volume 1. You even catch a glimpse of the flyer in the series, which reveals that Henry himself is starring in it.

But after watching Stranger Things Season 5, Volume 2, it turns out there are even more connections between the play and the show, each helping the other create a clearer portrait of Henry/Vecna's origin story. From Henry's fateful time in Nevada to some enlightening information about Eleven's (Millie Bobby Brown) own powers, here's how Stranger Things: The First Shadow illuminates the mysteries of Stranger Things Season 5, Volume 2.

Stranger Things: The First Shadow reveals why Henry is so afraid of the caves in his mindscape.

One of the biggest questions I had about Stranger Things Season 5, Volume 1 was why Henry was too scared to follow Max into the cave system in his memories. Lo and behold, Stranger Things: The First Shadow had the answer the whole time.

The play reveals that the cave system was where Henry first ventured to Dimension X — now dubbed "The Abyss" in Stranger Things. That's the alternate dimension where the Mind Flayer and Demogorgons are from, as opposed to the Upside Down, which Volume 2 reveals is a bridge connecting the Abyss to our world.

According to Stranger Things: The First Shadow, the Nevada caves in Henry's memory were home to experiments Dr. Brenner (Michael Modine) was running in order to learn more about Dimension X. His own father briefly vanished there during a World War II-era experiment on the USS Eldridge battleship. However, one of the scientists on his team defected to the Soviets. He stole some equipment from the labs and fled. During his escape, he crossed paths with Henry, at which point the stolen equipment transported them both to the Abyss.

Naturally, that dimension-hopping experience was traumatizing for Henry, explaining why he won't revisit those caves or memories in his mindscape. But while all of this is relayed through a speech from Dr. Brenner in Stranger Things: The First Shadow, Stranger Things Season 5, Volume 2 actually gives us a sneak peek at what happened to young Henry out in Nevada.

In episode 6, "Escape from Camazotz," Max and Holly (Nell Fisher) watch Henry's encounter with the defecting scientist. Initially, Henry wants to help the wounded defector, who's carrying a mysterious briefcase. But when the scientist shoots him in the hand — leaving a wound that Dr. Brenner mentions in Stranger Things: The First Shadow, but does not explain — Henry goes into fight-or-flight mode. He brains the scientist with a rock, the action starting as a survival instinct but quickly growing more bloodthirsty. Then, he goes to open the briefcase.

All we see of the case's contents is a rolling fog before Max and Holly continue on their way. But thanks to Stranger Things: The First Shadow, we know that whatever's inside the briefcase will bring Henry to Dimension X, where he'll come face to face with the Mind Flayer.

Don't expect that reveal to remain play-only knowledge, though. There's no way the Duffer Brothers would tease the importance of the Nevada memory without following through.

Stranger Things: The First Shadow explains why Henry and Eleven's blood is different.

Stranger Things Season 5, Volume 2 drops a pretty big bombshell about Eleven's powers. Throughout the show, she's believed she has her abilities because of her pregnant mother's involvement in the MKUltra program, which exposed Eleven to mind-altering drugs in the womb. However, it turns out her powers really stemmed from transfusions of Henry's blood.

In Stranger Things: The First Shadow, Dr. Brenner tells Henry that when his father reappeared from the Abyss, he had a completely unique blood type. The same exact thing happened to Henry following his exposure to the Abyss and the Mind Flayer.

The play features scenes of Dr. Brenner drawing Henry's blood, and we later learn why: It's to give to all of the kids being used in the Hawkins lab experiments. The transfusions impart Henry's powers to the children, all without exposing them to the Abyss themselves.

In Stranger Things Season 5, Volume 2, the U.S. government is attempting to recreate the success of those initial transfusions, this time forcing transfusions of Kali's (Linnea Berthelsen) blood into unconscious pregnant women. If they capture Eleven, they'd drain her blood as well. As Kali reasons, the government's insistence on seeing this program through means that neither she nor Eleven will ever be safe.

Stranger Things: The First Shadow's revelation that exposure to the Mind Flayer and the Abyss changes your blood type — and therefore likely gives you powers — adds a new wrinkle to Holly's plight. She, Derek (Jake Connelly), and the other kidnapped children have all been trapped within the Abyss, with Henry hoping to use them as vessels for his powers in order to join our world with his. However, if they do manage to escape this whole situation alive, will their powers remain? And will the government hunt them down in the way they did Kali and Eleven?

Unfortunately, that's not a question Stranger Things: The First Shadow can answer. Only the finale can do that.

Volumes 1 and 2 of Stranger Things Season 5 are now streaming on Netflix. The series finale premieres Dec. 31 at 8 p.m. ET on Netflix and in theaters.

Stranger Things: The First Shadow is now playing on Broadway and in the West End.