Warning: This article contains spoilers for Stranger Things 5, Volume 1.
Stranger Things 5 is further fleshing out Vecna (a.k.a. Henry, a.k.a. One) as a villain, and the first volume of the final season brings viewers directly into his mindscape via Holly Wheeler. This gives the show an opportunity to sneak in details from the Stranger Things: The First Shadow prequel play, which opened on London's West End in 2023 and is now playing on Broadway. The production digs deeper into Henry's backstory, and those familiar with it will pick up on references to the play in the new episodes. And according to Matt and Ross Duffer, viewers can expect more overlap between the Netflix show and the prequel in the finale.
In an interview with Variety, Stranger Things' creators were asked whether the cave where Max is hiding is the same one where Henry first comes into contact with forces connected to the Upside Down. After confirming as much, the Duffers explained their approach to balancing the contents of the play with the Netflix show. They also suggested that the remainder of season 5 will lean into the prequel further.
"There was always a balance that we had to find in terms of how much we were going to put in the play," Matt Duffer explained. "[The director] Stephen [Daldry] and [the producer] Sonia [Friedman] were always pushing for more and we were pushing back and saying, 'Well, we have to wait to reveal that in the show.' You’ll see, especially as you reach the final episode, there’s more overlap with the play."
Thus far, the references to The First Shadow in Stranger Things 5 are subtle; you don't need knowledge of the prequel to understand them. The revelation that Henry went to school with Joyce Byers won't come as a surprise to those who have seen the play. However, the latest episodes inform us of this connection by showing Max inside Vecna's memories.
We also see Henry chasing Max into the cave from the play in his mindscape, and he's noticeably afraid of the location. It's the reason Max is able to evade him for so long, and it likely stems from what he experiences there as a child. The First Shadow reveals that Henry once went missing in Nevada, and that he later resurfaced in this cave, where a dead Russian spy was also found. Henry has no memory of the incident, but it seems to be his first encounter with the beings of the Upside Down — and it's likely connected to the military base nearby.
Judging by the Duffers' comments, this history will be explained on-screen in Stranger Things 5's next two volumes. While the creators confirmed that the prequel will factor into the ending, they also promised viewers won't need to see it to make sense of what's coming.
Don't worry, you won't need to see the play to get Stranger Things 5's ending
Although Stranger Things 5's ending will feature more elements of the prequel play, fans shouldn't fret. The Duffers confirmed that you won't need to see the production to enjoy the conclusion. Matt Duffer told Variety, "[Y]ou absolutely do not have to have seen the play to understand. They’re Easter eggs more than anything."
This is a relief, as it would feel cheap to rely too heavily on an outside story to shape the Netflix series' finale — especially when that outside story is only accessible to watch in select locations. The recurring nods to the prequel are fun for those able to see The First Shadow. But by giving those unacquainted with its story more context, they offer the right amount of connections between the two projects.
What parts of Stranger Things: The First Shadow could be important in the finale?
With Stranger Things 5, Volume 1 emphasizing Henry's response to the mysterious cave, we can probably expect that to be the biggest source of overlap between the TV show and stage play. Henry's disappearance could be used to explain his dark turn and how the Upside Down influenced it. Some Stranger Things theories even posit that the Mind Flayer is controlling Henry and not the other way around. If he does prove to be a pawn in a greater villain's game, the cave could be where he meets that entity. It would certainly explain his reluctance to go into it again.
The fact that Henry went to school with Joyce may also prove important, as it would add another layer to Will's kidnapping. With Henry and Joyce knowing each other previously, it's possible the villain went after her son for a reason. We won't know for sure until Stranger Things returns on December 25 and December 31. The First Shadow gives fans plenty to speculate about, though, even if they haven't seen it firsthand.