A.S. Byatt's "The Thing in the Forest"

When I first read the story, and heard the first descriptions of the "thing" I immediately thought the "thing" was what the girls were experiencing and their own way of making sense of all the questions they had. The train they were on was described as it "crawled sluggishly" and not being clean and had a "dank smell of unwashed trousers." That sounds a lot like the characteristics of the "thing."
Back to the "thing." It also makes me imagine war. When they describe the "thing" it sounds like anything that it comes in contact with gets wrapped up in it. It had wire, vegetation, meat, dishcloths, and wire wool all entangled in it. Just like war, it engulfs everyone and everything. Nothing is left unchanged after war. The struggles that families, and especially kids, go through are abundant and I'd imagine, much like Penny and Primrose, they find a way to make sense of their struggles and a way to cope with them. The "thing" is how Penny and Primrose make sense of their situation.
The narrator takes time to point out that Penny and Primrose are very different, but are very much alike. The narrator does the same with the two mothers. I'm not sure exactly why the narrator keeps pointing it out, but maybe to show that in times of distress, no one knows exactly what to do or how to cope with it.
I like all the personification that the narrator describes everything with. Giving the train characteristics to describe how it is moving really sets the scene in my head. The description of the "thing" was very well drew out to give you a good picture of what it looked like.