In the authorised Miss Marple continuation short story The Open Mind, Jim the butcher's boy is a St. Mary Mead villager mentioned by Miss Marple as a village parallel. Jim wanted to impress a girl named Betsy and couldn't wait for her to notice him of her own accord and so he bet that he could jump across the mill race. He failed and fell into the water. Miss Marple mentions Jim as an example of the impatience of youth that she sees as characterising some of the events in the story.
Later Jim accused a farm hand of having greased the rocks. This is a second parallel to what Miss Marple observes in the events in the story. There is a tendency to become obsessed with the idea that there is a grand conspiracy, that everything is intended that there are "secret powers moving behind all the scenes". Of course the rocks were not greased. "There is no secret that everyone knows but you". Things just happen because they happen, often in a boring, simple way.