What is the plot of "A Clean, Well-Lighted Place"?

Honestly, I would say that this question doesn't really apply. By that I mean, the story is so brief, and depends so heavily on mood, that I would argue it doesn't have a fully developed plot in the sense of one event leading causally to another. In fact, the plotlessness fits with the story's themes. Look at the lines late in the story where one man is thinking on the nothingness of life: "… Our nada who art in nada, nada be thy name thy kingdom nada thy will be nada in nada as it is in nada…"

Nada = nothing, which means, also, no plot.