A prisoner in jail receives a letter from his wife:
I have decided to plant some lettuce in the back garden. When is the best time to plant them?
The prisoner, knowing that the prison guards read all mail, replied in a letter:
Whatever you do, do not touch the back garden. That is where I hid all the money.
A week or so later, he received another letter from his wife:
You wouldn’t believe what happened, some men came with shovels to the house, and dug up all the back garden.
The prisoner wrote another letter back:
Now is the best time to plant the lettuce.