When a local boy, Will, goes missing, his middle school friends poignantly launch their own investigation. Coincidently, A girl with no memories wanders down the same road, Mirkwood, where the local boy disappeared.
She is strong and vulnerable, an interesting contradiction. Mike, one of the kids looking for Will, shelters her in his basement.
Local police believe that Will has fallen into the quarry and accidently drowned. Joyce, the boy's mother, believes she can speak to him through a string of Christmas lights. Naturally, everyone surmises she's gone nuts with grief
For a plot like this, it would be easy for the series to fall into commonplace horror. The monster that chases them in the upside down is fairly classic horror--cobwebs, stickiness, facelessness.
Stranger Things doesn't descend, however, into comic book characterizations. Not all of the bad characters are entirely bad e.g. Steve, nor all of the heroes entirely good e.g. Hopper.
As in every work of horror, there is something terrible in the ordinary. Take nothing for granted, the genre seems to say.
Even the most polished, the most exemplary may be hiding a dark secret. Conversely, even the weakest or the most vulnerable may be strongest.