The Contents of that Case Henry Unlocks in Stranger Things?
During the bulk of the fifth and final season of *Stranger Things*, the young Holly Wheeler and Max are imprisoned inside a mental fortress constructed from the recollections of Vecna. Their quest for a way out in the pivotal sixth episode leads them to relive a traumatic incident from Henry's childhood—an event that potentially carries the means to overcome him for good.
Spoiler Warning: This discussion contains major spoilers for the concluding episodes.
The Discovery in the Cavern
When she finds Max in the mental landscape known as Camazotz, it becomes clear she is hiding out in a cave that Henry is terrified of. An accidental discovery a telescope pilfered from Henry's old home allows Holly to realize that the true terror lies not within the cave. Matching her view to the cut-out, she and Max plummet into a subterranean passage.
There, they witness a young, eight-year-old Henry come across an wounded, fearful individual. As the boy offers aid, the man panics and shoots, striking Henry in the hand. To protect himself, Henry ends the threat with a rock. "Was this the turning point?" Holly wonders aloud. The answer is affirmative, but the trauma involved more than a fight for life.
Like many elements in volume 2, the full story behind the mine shaft incident is detailed in the live show the prequel play.
The Philadelphia Experiment and Stolen Research
This backstory explains the infamous Philadelphia Experiment, which transported a U.S. Navy ship into a dimension later called the Abyss. Demogorgons assaulted it, and the only one to return was the ship's commander, who came back in a catatonic condition with an altered blood type.
The captain's son, the future Dr. Brenner, sought to replicate this experiment in Nevada. But a disloyal lab worker stole research materials to give to the Russian agents, who were eager to begin their own interdimensional projects. The man in the cavern is the one who stole the materials.
So, What's in the Case?
Based on what is revealed about his research, the case almost certainly contained some of Captain Brenner's infected blood. In the scene, Henry is wounded and bleeding. Exposure likely occurred upon contact with the blood, causing the development of his psychic abilities—traits he would genetically impart to the test subjects under Brenner's care.
A second theory, the case could have held strange particles that later made its way to the Hawkins lab, where it acts to anchor the mirror dimension. The stage play explains that young Henry ended up in the Abyss, coming back after half a day as a different person. Throughout the play, he struggles with the influence of a malevolent force, reminiscent of how Will was possessed by the Mind Flayer in the past.
A Weaponized Emotion
His lasting fear associated with the mine demonstrates how deeply scarring the incident was for him. While he orchestrates the Hive Mind and attempts to pull the Abyss into Hawkins, a piece of the scared boy remains. Fear is his tool, and the series is building toward a final confrontation between him and Will, who has confronted his greatest terrors to become stronger.
His confrontation has effectively disarmed Vecna. Furthermore, Will now knows what Vecna himself fears, which could provide a decisive edge in the endgame conflict ahead.
