This is one of the rare "good" "Bonanza" episodes. The Cartwrights are largely absent, with no meaningful role in the story. Almost all the focus is on Mrs Wharton, a wealthy Englishwoman touring the world. There's nothing cowardly or reticent about her, and she's confident she knows best how to handle any situation.
Mildred Natwick was primarily known for Broadway and movies, her best-known roles in the latter being Miss Gravely in "The Trouble with Harry" and Griselda in "The Court Jester". "Mrs. Wharton and the Lesser Breeds" is one of her rare TV appearances, giving us something not often seen on TV -- first-rate acting.
Natwick commands our attention by consistently underplaying. She has a sentimental but well-written monologue in which she recounts the important moments of her life. It works because she holds back, which makes her all the more convincing when she talks back to Candy at the end. She brings class to a generally lame TV series.
The late Jesse Pearson ("Ed") is best known for playing Conrad Birdie.