One day, prisoner received a letter from his wife, "Dear Husband, I have decided to plant some lettuce in the back garden. When is the best time to plant it?"

The prisoner, knowing that the prison guards read all mail, wrote back, "Dear Wife, whatever you do, do not touch the back garden. That is where I hid all the money."

A week later, the prisoner received another letter from his wife, "Dear Husband, I am so happy. You wouldn't believe what happened. Some men came to the house with shovels, and dug up the back garden."

The prisoner wrote another letter back, "Dear wife, now is the best time to plant the lettuce."