In the novel N or M?, Sophia Minton is one of the guests at the Sans Souci in Leahampton. She is described as an elderly woman, thin and angular, with a neck that is "stringy". She wears chains or necklaces of beads. She is often seen knitting items of khaki wool to help with the war effort or volunteering at a depot packing parcels for the troops at the front.
Miss Minton wears "pale sky-blue jumpers", and her skirts are "tweedy", with a "depressed droop at the back".
When Tuppence first arrives at Sans Souci, she tells Miss Minton that she never sleeps well the first night or two in a strange bed. Miss Minton says that it is exactly the same with her. Miss Minton also helps Tuppence with her knitting, saying that it is no trouble, as she has knitted for so many years.
When some of the female residents of Sans Souci play bridge together, Miss Minton talks a lot, making "ceaseless reiterations". Tuppence thinks to herself that it would save time if Miss Minton puts her hand down on the table to show all her cards, as she is "quite incapable of not telling" what is in her hand. Miss Minton also looks with "unabashed interest" into Mrs Sprot's hand.
The ladies later begin discussing Mrs Perenna, who had just been seen coming in. Miss Minton wonders where she had been. Such "small wonderments" are a big part of life for her. Miss Minton also asks the other ladies if they think that Mrs Perenna drinks.
Miss Minton has a cousin named Selina, whom she mentions when Tuppence is telling her about Aunt Gracie. Miss Minton is interested in the symptoms which Aunt Gracie suffers, and compares them to those suffered by Selina.