The School Train

I had my childhood train set laid out on the floor of a big barn.
It ran from a station uphill to the door at the top of the barn.
Powered by clockwork, it looked good and worked well.
As I was looking at it I caught a movement out of the corner of my eye. It was a tiny child running to catch the train. More followed and boarded the train. All wore school uniform and had schoolbags.
Then, without me touching it, the train moved off and trundled along, up to its destination. I watched as the children disembarked and run out of the top barn door.
The train waited at the top station presumably for the schoolchildren when they came out of school.
The whole episode didn't seem that odd and I was pleased that the train set had some use.
Then the barn filled with wasps, not so pleasing.
Some balance law had asserted itself.