It doesn’t make any sense and has a lot of loose ends. They don’t explain how the guy with the briefcase came to aquire a piece of the mind flayer and how he knew that it would consume Henry insinuating that he knew what it was before any of the testing they had done on psychic kids because that moment is what made Henry what he was. Dustin determines that scientists created the upside down, but also the abyss is a “planet” in the upside down and also that’s where the mind flayer resides. In a place that was created by humans??? Wtf is with this fucking plot? They insinuate many times that everyone who has psychic powers is just tapping into the mind flayer’s hivemind powers yet after they kill it they still have powers. How does that make any fucking sense? Overall it was fine, it was just really fucking stupid.