Throughout season 5, Max, Holly, and other children kidnapped by Henry/Vecna hide in a cave he is scared to enter. In the TV show, Henry relives the traumatic memory of finding a scientist in that cave, killing him in self-defense, and opening a briefcase filled with matter that gave Henry his supernatural powers. But The First Shadow reveals more to the story.

The play opens on the warship USS Eldridge, an actual ship that was the subject of a teleportation hoax. Here, Dr. Brenner's father was the ship's captain, who was actually teleported to an alternate dimension and came back changed. Brenner himself sought out to reach that place, dubbed Dimension X, and replicate what happened to his father.

Another scientist on Brenner's project stole some of its technology and brought it to a cave in Nevada, where the Creels were living at the time. In the play, when Henry finds the scientist and opens the briefcase, they're transported to Dimension X, where the Mind Flayer infects Henry.

As Henry declares in the TV show, he embraces the Flayer's dark influence, even though he initially fights it.

But how did Brenner come to find Henry from there? The spyglass is key to the answer. In The First Shadow, we learn that when Henry found the scientist in the cave, he was playing with a spyglass — the same one Holly and Max use to find the path out of the cave and through Henry's memories in season 5.

Henry dropped the spyglass in the cave when he was transported to Dimension X, and Dr. Brenner found and used it to track him down. That's how Henry came to Brenner's lab, and the doctor began his experiments: testing Henry's powers, connecting him to Dimension X, and using his blood to create more superpowered kids like Eleven.

When Holly and Max first enter Henry's memories in season 5, they're in a bustling school hallway, where a young Joyce is flyering for the production of Oklahoma! she's directing at Hawkins High. Later, Max and the kids escape Henry's mind through a memory set while the performance is going on.

Eagle-eyed viewers might have thought the dark, creepy production in that memory doesn't look much like Oklahoma!, and they'd be right. Joyce, without the school's knowledge, is actually staging an obscure play called Dark of the Moon, starring Henry and Patty Newby (the sister of season 2's Bob Newby) as a “witch boy” and the ordinary girl he loves. The plot mirrors the teenagers' own romance.

The performance is a weighty memory for Henry because Brenner shows up and disrupts it, believing Henry's affection for Patty keeps him from advancing Brenner's experiments.

Take a closer look at the cast list on Joyce's Oklahoma! flyer. They include Hopper, Karen Childress and Ted Wheeler (Holly, Mike, and Nancy’s parents), Alan Munson (the dad of season 4's Eddie Munson), and of course, Patty and Henry.

The play is set in the '50s, when they were all in high school together alongside even more of the adults in the TV show. Not only will you recognize various future spouses (like the Wheelers), you'll also discover the history between other characters, like Joyce and Hopper, that foreshadows their relationships as adults.

Here's a fun bonus crossover between the Netflix show and the stage show. TV viewers will recognize Alex Breaux as Lieutenant Robert Akers on Stranger Things season 5. But did you know he also plays a younger Dr. Brenner in Stranger Things: The First Shadow on Broadway?

This isn't a hidden Easter egg; Breaux's stage and screen roles aren't connected in any way. But just as Stranger Things spans multiple dimensions, Breaux's career with the franchise stretches across multiple mediums.

Get Stranger Things: The First Shadow tickets now.

Photo credit: Stranger Things: The First Shadow on Broadway. (Photos by Matthew Murphy and Evan Zimmerman)