The Contents of that Briefcase Henry Opens in the Hit Series?
Throughout a large portion of the fifth and final season of the popular Netflix show, the young Holly Wheeler and Max Mayfield find themselves trapped inside a mental fortress built from the recollections of Henry Creel. Their mission for a way out in "Escape from Camazotz" forces them to relive a defining event from Henry's early years—a discovery that potentially carries the key to defeating him permanently.
Spoiler Warning: This article details significant events for the concluding episodes.
Unearthing the Secrets of the Tunnel
When she finds Max in the psychic realm called Camazotz, Max reveals she is sheltering in a chamber that Henry is terrified of. A clever observation a spyglass pilfered from Henry's old home lets Holly see that the source of fear lies not within the cave. By aligning her view through the cap, she and Max tumble into a deep mine shaft.
There, they witness a child version of Henry come across an man who is hurt and scared. Attempting assistance, the man panics and shoots, wounding the boy in the hand. In a desperate act of self-defense, Henry strikes the man down with a rock. "Did this make Henry evil?" Holly wonders aloud. The answer is affirmative, but the event wasn't just a simple act of survival.
Similar to other plot points of the final season, the truth about the events in the tunnel was first explored the theatrical production the prequel play.
The Philadelphia Experiment and A Spy's Mission
This backstory explains the 1943 event, which reportedly teleported a U.S. Navy ship into a plane known as the Abyss. It faced creatures, and the only one to return was the ship's commander, who came back in a vegetative state with an altered blood type.
This man's son, a young Martin Brenner, sought to replicate this dimensional breach in Nevada. However, a treacherous employee pilfered lab samples to hand over to the Communist spies, who were keen to start their own interdimensional projects. The man in the tunnel was that very thief.
The Briefcase's Contents
Based on what is understood of the doctor's experiments, the case most likely held vials of the unique blood type. As shown, Henry is wounded and bleeding. Exposure likely occurred upon contact with the blood, causing the origin of his telekinetic gifts—traits he would later pass on to the children Brenner would experiment on.
Alternatively, the case could have held exotic matter that was destined to travel to the secret facility, where it maintains the stability of the Upside Down. The prequel shows that Henry somehow wound up in the Abyss, reappearing 12 hours later fundamentally changed. As a youth, he battles the control of a dark entity, reminiscent of how Will was possessed by the Mind Flayer in an earlier season.
Confronting Terror
His lasting fear associated with the mine shows how deeply scarring the incident was for him. Even as he commands the Hive Mind and works to collapse the Abyss into Hawkins, a piece of the scared boy lingers. The villain weaponizes terror, and the show is setting up a final confrontation between the monster and Will, who has confronted his own deepest fears to fortify himself.
This journey has effectively disarmed Vecna. More importantly, Will now understands what his enemy truly fears, potentially giving him a decisive edge in the series finale to come.