The Monkey's Paw
We never learn Mr. and Mrs. White's first names. They are only called Mr. and Mrs. White or "mother" and "father." This is stresses their identities as a married couple, parents, family people, and heads of a household. When Herbert dies, all aspects of this identity are challenged. They have no idea how to act without their son in their lives.
One of the first things we are told about Sergeant-Major Morris is that he is "beady of eye" (1.10). This means he looks sneaky, like he has something to hide or has a trick up his sleeve. This sets the reader up to mistrust Morris. It also shows that the narrator sees things in him that the characters might not. The Whites seem impressed by him, while the narrator suggests that he doesn't appear trustworthy. All this makes Morris a mysterious, ambiguous character; as with the paw, we are never quite sure what to make of him.
Take a look at "Characters" to read about Herbert's physical appearance and how it changes throughout the novel.