How Stranger Things Season 5 Connects To The Stage Play The First Shadow

This article contains spoilers for the first four episodes of "Stranger Things" Season 5.

Fans searching for hints on what to expect from upcoming episodes of "Stranger Things" may want to look to an unlikely source — live theater.

In the interim between "Stranger Things" Season 4 and Season 5, a spin-off play started running, first on London's West End and later on Broadway. The play was written by Kate Trefry, but The Duffer Brothers were closely involved in the story, which is official "Stranger Things" canon.

For a few years, the stage show "Stranger Things: The First Shadow" was the only major source of new material in the franchise. It focuses on the backstory of Henry Creel, aka Vecna (Jamie Campbell Bower on Netflix), and the high school lives of Joyce Byers (Winona Ryder on Netflix) and Jim Hopper (David Harbour on Netflix). 

There are a number of details in "Stranger Things" Season 5, Volume 1, that will leap out at those who have seen "The First Shadow." Most of these tie-ins occur in the dream realm where Vecna imprisons Holly Wheeler (Nell Fisher). When Holly encounters Max (Sadie Sink), she explains that the world they're trapped in is made up of Henry's memories, including a 1959 Hawkins High School flashback that pulls directly from the events of the play. Theatergoers may also recognize the Nevada caves where Max makes her hideout from the prequel play.

Max tells Holly that the cave they're hanging out in is safe because, for some reason, Henry won't enter it. Whenever he gets close, he appears to be overcome with terror. If you've seen the play, you know exactly why.

During his childhood, Henry and his family live close to a military facility in Nevada that conducts top-secret tests on interdimensional energy. While exploring in the nearby caves, young Henry stumbles across misplaced technology that transports him to Dimension X — aka the birthplace of the Upside Down — where he encounters the Mind Flayer and experiences severe changes at a molecular level.

It's also worth noting that the spyglass Holly uses on her expedition, taken from a memory of the Creel House, is likely the same one Henry uses in the play. As an added Easter egg, when Max recalls experiencing Henry's high school memories from 1959, we see Joyce handing out flyers for a production of "Oklahoma!" — another plot point from "Stranger Things: The First Shadow."

While we don't get there in the first four episodes of Season 5, it seems like we're building toward a more complete understanding of the relationship between Dimension X and the Upside Down. Up to now, "The First Shadow" has provided the clearest explanation of Dimension X as a separate-yet-related dimension to the Upside Down.

While the two realms share the presence of creatures like the Demogorgons, they're not difficult to tell apart — the Upside Down is mostly blue and a recreation of Hawkins; Dimension X is a red-orange hue and features only barren alien landscapes. Some longstanding "Stranger Things" theories suggest that the Upside Down could be a far-future version of Hawkins — an idea bolstered by references to "A Wrinkle in Time" in Season 5. Either way, it seems possible that we'll get a more concrete explanation of the two dimensions in the final four episodes, which would make good on the worldbuilding hints dropped in the stage play.

"We do even a little more with the play in a later episode," Ross Duffer said in a recent interview with The Wrap.