In Episode 4 of Stranger Things Season 5, Max tells Holly how they are inside a memory within a world of thousands of memories, created by Henry. When she first gets there, she discovers there are only three choices: take their own life, accept whatever may happen to them, or try to escape.

When she tries to escape, Henry finds her, running after her. Scared, she hurriedly enters a cave. However, it is odd when Henry appears terrified of the cave and does not chase after her. As fans may have guessed, the cave is not a random location but has direct ties to Vecna’s traumatic origins.

The prequel play, The First Shadow, reveals that this cave is where young Henry first came into contact with dark, interdimensional forces, marking the beginning of his tragic transformation. According to the play, Henry was 8 years old when he ended up wandering into the cave in Nevada.

There in the cave, a Russian spy had stolen some tech from Brenner’s lab and had hidden in the cave. After Henry toyed with the hidden tech, he was accidentally teleported to the Upside Down. This shows his traumatic origin as Vecna, how he got his powers, and his connection with the Mind Flayer.

Matt Duffer Confirms Max’s Cave is the Same One

Following the release of the first four episodes of Season 5, Matt and Ross Duffer spoke to Variety about it. When asked if the cave is a reference to the Stranger Things prequel play, Matt confirmed that it is the same cave that led to Henry’s turn as Vecna.

Yeah. When we were working on the play with Kate Trefry, we had Henry’s backstory worked out. There was always a balance that we had to find in terms of how much we were going to put in the play. [The director] Stephen [Daldry] and [the produce] 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.’

In short, the cave isn’t just a new plot device, but it is a long-planned piece of lore. Its reappearance in Season 5 is the first time the show draws a direct line from Henry’s traumatic origin to the present conflict.

Watching The First Shadow is Not Important for Season 5

Despite the strong connections, the creators emphasize that you do not need to watch the play to understand Season 5. Matt revealed that as we inch closer to the final episodes, there will be more and more overlap with the play, but maintained that there is no need to watch the play.

But you absolutely do not have to have seen the play to understand. They’re Easter eggs more than anything.

While we will have to wait and see how the show and the play will connect, there is one conflict between the cave story. As we previously saw in the show, Eleven, when enraged, uses her powers and accidentally opens the gate to the Upside Down.

She banishes Henry to the world, leading to his transformation as Vecna. Together with these two stories, the show might explain how Henry got under the control of the Mind Flayer and his origins as Vecna.

Hence, the cave story ties government experiments, Dimension X, and the Mind Flayer directly to Henry’s backstory, linking all origin threads into one long narrative arc before it all comes to a conclusion.

The next episodes of Stranger Things Season 5 will be released on December 25, 2025, only on Netflix.