Stranger Things season 5 cave explained: what is it, how does it connect to the Upside Down, and why is Vecna scared of it?

Three years after Eleven very nearly destroyed Vecna in Stranger Things season 4's dramatic finale, Henry Creel is back and stronger than ever in Stranger Things season 5. But even though we don't see the burned creature until the mid-season finale's very last moments, the first few episodes shed some light on what is going on inside Creel's head (quite literally), which may be a big hint as to how he can be destroyed.

Warning: major spoilers follow for Stranger Things season 5 volume 1, so turn back now if you haven't seen it, and check out our Stranger Things season 5 volume 1 review.

Surprisingly, the first half of season 5 shows a lot more of Vecna in his human form than as the charred looking monster Eleven turned him into. That's because he spends the majority of his time as Holly's imaginary friend Mr. Whatsit. As part of his master plan to kidnap 12 children (for more on that, read our Stranger Things season 5 volume 1 ending explained), Vecna manipulates Holly, promising to save her from the monsters in order to gain her trust. Then, he has her kidnapped by a Demogorgon, taken to the Upside Down, and hooked up to one of his disgusting feeding tubes.

But while Holly's body lays unconscious in the Upside Down, her subconscious is wandering around Creel's mindscape, living at a perfect version of his house from the '50s, totally unaware of what is actually happening to her. One day, Holly receives a letter from Henry, telling her to meet in at the spot marked X. There she finds Max, who has been hiding out in Henry's mind since he put her in a coma in season 4. Max tells Holly all about Vecna and explains that she is locked in his memories now.

Max shows Holly that she has made a hideout in a cave, the only place Vecna will not go. In fact, he is terrified of it. In a flashback, we see him chasing Max, but when she runs into the cave, he just stands at the entrance looking petrified. When he reaches his arm out to her, the limb is burned and corpse-like, like his Vecna state. So, what is the cave, and why is Vecna so scared of it?

What is the cave?

Although many of us are as in the dark as Max and Holly about what the cave actually is, those who have seen the West End and Broadway play, Stranger Things: The First Shadow, may be a little more clued in. Set in 1959, the show is essentially Henry Creel's origin story, taking audiences back to when the Creel's first moved to Hawkins, where Henry commits his horrendous crimes, leading him to Dr. Brenner (aka Papa).

However, the show also touches on the cave, a detail that many audience members may not have even noticed. Near the start of the show, we learn that on Henry's eighth birthday, he went missing for 12 hours near a military base in Nevada and was eventually found outside a cave with no memory of what had happened. However, later on, it is revealed that while Henry was missing, a Russian spy was found dead in the same cave system, suggesting that he had come to the US through the Upside Down. Although it has never been confirmed, Henry could well have ventured into the Upside Down and might have first made contact with the Mind Flayer.

So, if the cave leads to the Upside Down, why is Henry so scared of it? It could remind him of his childhood trauma, and so Vecna may be worried that if he were to enter the cave again, he may reconnect with his humanity and cease being the fearsome creature hellbent on destroying Hawkins and the world. However, in season 5 episode 4, he did look genuinely scared of the cave, so we think the system might hold something way more malevolent.

Is the cave or Henry's memories part of the Upside Down?

If the cave system is the same one from The First Shadow, that means it is connected to the Upside Down. This, in turn, means that although Max and Holly are trapped in Henry's mind, if his memories are being held in the Upside Down, the two may have a chance of finding Dustin, Steve, Nancy, and Jonathan, who are also currently in the underworld. So, if Henry's mindscape is in the Upside Down, where is it?

As Will knows every inch of the Upside Down thanks to his time spent down there and his connection to Vecna, you'd think we would have come across Henry's memories. However, there are some undiscovered parts of the Upside Down where Vecna could be hiding his mindscape, like behind the wall.

What is behind the Wall?

One of the biggest mysteries in Stranger Things season 5 volume 1 is the huge wall in the middle of the Upside Down. The tall, fleshy wall is first discovered by Hopper and Eleven, who find it blocking their way to the other side. The two see it wince as a soldier pees on it, and later an injured Demogorgon limps towards it. The wall seems to be alive, made up of the same matter as the other creatures in the Upside Down. In one scene, Dr. Kay takes samples from one of the big balls of pus pulsating on it. However, later, when Dustin, Nancy, Steve, and Jonathan arrive in the Upside Down, they find the same wall, but on the other side of the Upside Down. With help from the very clever Dustin, we learn that the wall is actually a circle, hiding something inside.

We can't help but wonder what the wall's significance is, but Dustin seems sure that Vecna is hiding Holly behind it. If that were true, that would mean that Henry's memories (and the cave) are inside the wall. If Vecna is trying so hard to protect something, it must be dangerous enough to destroy him. Could the cave lead to Vecna's demise? We will have to wait and see.

Stranger Things season 5 volume 1 is out on Netflix, with volume 2 set to arrive on Christmas Day. See our Stranger Things season release schedule for exact timings. For more, check out our list of the best Netflix shows to stream right now.