This episode's title at first thought applies to Will, because after all it's him that the line of dialogue to spoken to. But in reality, it could be stretched to apply to most of the cast, who are isolated in some way or don't fit in. Apart from the obvious one being Will, Eleven also feels isolated, as she has to stay cut off from society in Hopper's place. She can't even speak to Mike, although she tries to. Nancy is struggling to fit back into normal life after the previous season's events leading to Barb's tragic ending. Meanwhile, John is literally a freak in many people's eyes. Then there's Max. We don't really know who she is yet, but she definitely doesn't fit in, nor does she seem to want to.
There weren't many major events in this episode and the alien threat of this season wasn't developed much further, but it gave further insight into the characters that made it gripping, and sad, to watch.
There weren't many major events in this episode and the alien threat of this season wasn't developed much further, but it gave further insight into the characters that made it gripping, and sad, to watch.