A farmer has a watermelon patch and after inspection finds that some of the local kids have been helping themselves to a feast.
The farmer thinks of ways to discourage this profit-eating situation. So he puts up a sign: "WARNING! ONE OF THESE WATERMELONS CONTAINS CYANIDE!
He smiled smugly as he watched the kids run off the next night without eating any of his melons.
The farmer returns to the watermelon patch a week later to find that none have been eaten, but finds another sign that reads "NOW THERE ARE TWO!"