Things Have Changed
Thurber modernizes an old story what every has read or heard. It has to do 
with a nefarious wolf who kept a vigil in an ominous forest until a little
girl came along carrying a basket of food for her grandmother. With alacrity,
this vivacious youngster told the wolf the address to which she was going.
Hungry and gaunt the wolf rushed to the house. When the girl arrived and entered
,she saw someone in bed wearing a nightcap and nightgown. While the figure was
dressed like her grandmother, the little girl surmised with only a perfunctory
glance that it didn't have the old lady's mien. She approached and became
cognizant of the hirsute of the wolf. She drew a revolver from her purse and
shot the interloper dead. Thurber arrives at a moral for this story that anyone
would find difficult to refute:It is not so easy to fool a little girl as it
used to be.

to leave no stone unturned--to try one's best, to make every effort.
Since you're from Missouri, I'll leave no stone unturned to convince you.