@samsonjasIf non-Americans have only a fuzzy idea, it's the same with Americans.
There's no real meaning, and nobody really cares, it's currently just an excuse to buy some candy, and hope no kids show up so you can eat it all yourself.
Many years ago when people actually lived on farms, it was a good time to celebrate a harvest festival - cool nights, hay rides, bonfires, and chances for young people to match up...
And relatively recently, in cities, it has turned into an opportunity for yuppies to wear sexy costumes, get drunk and do stuff that they may regret in the morning.
Observation seems to vary regionally. For example, where I live now, not a single "trick-or-treat" kid (or adult) has shown up in the past 40 years. Other places, kids still go from door to door (accompanied by "helicopter parents" of course).
If you go back to the Scottish and Irish roots, you find "neeps lanterns" and the practice of dressing kids up in scary costume to ward off evil spirits. Those have been imported to the US due the the large number of Irish and Scots who immigrated here.
All of this started in Europe, specifically Ireland, Scotland and England, long before the US existed. Don't know why it should be little-known there.
Same applies to Thanksgiving, which is just a harvest festival imported from Germany, Norway, and probably every other area that was successful in growing enough food to store for the winter.
Once the cider ferments, what else to do but have a party?
But to answer the original question, the answer is no. Halloween being mostly vague and meaningless in the US, writing an interesting story based on that doesn't seem practical.
Maybe one set in a scary Edinburgh castle... but then, non-American readers would have to be familiar with their own history, otherwise it's still going to take a lot of explaining.