Throughout a large portion of the fifth and final season of the popular Netflix show, the young Holly Wheeler and Max Mayfield are imprisoned inside a mental fortress constructed from the memories of Vecna. The search for freedom in the pivotal sixth episode forces them to relive a traumatic incident from Henry's childhood—a moment that potentially carries the secret to his downfall for good.
Editor's Note: The following reveals crucial plot points for the concluding episodes.
The Discovery in the Tunnel
Upon meeting Max in the mental landscape called Camazotz, Holly discovers she is taking refuge in a cave that Henry avoids at all costs. By leaving the lens cap on a spyglass taken from Henry's old home allows Holly to realize that the danger lies outside of the cave. Matching her view through the cap, she and Max plummet into a subterranean passage.
There, they witness a young, eight-year-old Henry find an man who is hurt and scared. Attempting assistance, the man reacts violently, hitting him in the hand. In a desperate act of self-defense, Henry ends the threat with a rock. "Was this the turning point?" Holly asks tearfully. The answer is affirmative, but the trauma went deeper than a fight for life.
In keeping with mysteries in volume 2, the full story behind the encounter was first explored the stage play Stranger Things: The First Shadow.
A Naval Mystery and Secret Science
This backstory explains the 1943 event, which reportedly teleported a vessel into a dimension dubbed the Abyss. The ship was attacked, and the sole survivor was the captain, who returned in a catatonic condition with an entirely new blood.
This man's son, a young Martin Brenner, wanted to repeat this phenomenon in Nevada. However, a treacherous employee took experimental components to give to the Russian agents, who were eager to begin their version of the tests. That traitor in the mine shaft is that employee.
The Briefcase's Contents
Considering what is known about Brenner's work, the case almost certainly contained some of the altered blood. At that moment, Henry is already bleeding. He likely becomes contaminated upon contact with the blood, which triggered the development of his psychic abilities—abilities he would genetically impart to the test subjects under Brenner's care.
A second theory, the case could have held dark matter that eventually found its way to the secret facility, where it maintains the stability of the Upside Down. *The First Shadow* reveals that the boy was transported in the Abyss, returning after half a day as a different person. From then on, he fights the control of a sinister presence, reminiscent of how the character Will was controlled by the shadow monster in the past.
The Power of Fear
The reason Henry avoids the cave linked to that memory demonstrates how profoundly traumatic the incident was for him. Even as he orchestrates the army of monsters and works to collapse the Abyss into Hawkins, a part of him lingers. The villain weaponizes terror, and the series is building toward a final confrontation between him and Will, who has confronted his personal demons to fortify himself.
His confrontation has taken a weapon from Vecna. More importantly, Will now knows what the monster's own weakness, which could provide a decisive edge in the series finale that awaits.
