At school Lil' Johnny was told by a classmate that most adults are hiding at least one dark secret, and that this makes it very easy to blackmail them by saying, "I know the whole truth."

Lil' Johnny decided to go home and try it out. He went home, and as he was greeted by his mother he said, "I know the whole truth." His mother quickly handed him $20 and said, "Just don't tell your father."

Quite pleased, the boy waited for his father to get home from work, and greeted him with, "I know the whole truth." Johnny's father promptly handed him $40 and said, "Please don't say a word to your mother!"

Very pleased, the boy was on his way to school the next day when he saw the mailman at his front door. Lil' Johnny greeted him by saying, "I know the whole truth."

The mailman immediately dropped the mail, opened his arms saying, "Then come give your real father a big hug."