In the novel N or M?, Charles is a friend of Deborah Beresford.
Charles is described as being a fair-haired young man. At the end of the novel, he dances with Deborah at a party hosted by Tommy and Tuppence.
Earlier in the novel, Deborah had mentioned someone named Charles. At the time, she had believed her mother to be in Cornwall visiting Aunt Gracie, and as Charles was going to be visiting his people in that area, she asked him to go and see her mother. Charles had gone, and had found that Tuppence was not there, and had not been there at all. However, it is not clear whether this is the same Charles or not.