8 Unanswered Questions From Stranger Things Season 3

8. Who Were The People In The Upside Down?

The Upside Down, a dark and deathly parallel dimension to our reality, wasn't featured as heavily this season. The Mind Flayer managed to wreak his havoc in the real world, thanks to the Russian subplot in Hawkins. The few scenes shown of the Upside Down occurred in a couple of episodes, as Billy Hargrove found himself wandering through there after his first confrontation with the Mind Flayer.

It was during these scenes that Billy interacted with, seemingly, a doppleganger of himself. This mirror image seemed to represent the Mind Flayer's presence in Billy's mind, but who were the other people in the background behind Upside Down-Billy?

It is possible that the Mind Flayer had simply already managed to ensnare more Flayed victims and they too could have represented the minds the entity had trapped. Could it be possible, however, that was something else mysteriously represented? It is highly unlikely any of the people possessed by the Mind Flayer, in an homage to Invasion Of The Bodysnatchers, could return considering their grisly end. Could there be other people trapped in the Upside Down, however? And if so, does that mean certain characters thought to be lost could come back?