In the short story Accident, Mary is the maid of the the Merrowdenes who live in an English country village. The absent-minded professor has the habit of using his wife's china-tea bowls for his chemistry experiments. His wife chides him for this dangerous practice because the bowls get mixed up with those actually used for serving tea and Mary never washes them thoroughly unless there is a sign of some obvious residue in them. Merrowdene retorts that Mary has no business taking things out of his laboratory but his wife counters that they have tea so often in the laboratory anyway so it cannot be helped.
On the day of the key events in the plot, Mary was away from the house at the village fete.