I don't know if the mother has the secret or not, but at least she guesses it.
"The Eye of Dread"
Payne Erskine
"Yes-you'll never guess, if I give you a hundred guesses-it's most exciting-come along-" Peter was led away.
"Fortitude"
Hugh Walpole
That boor knows-guesses-nothing of the truth.
"Only One Love, or Who Was the Heir"
Charles Garvice