An old man digging potatoes

An old man named Billy Bob lived alone in the country. He wanted to dig his garden for his potato crop but it was very hard as the ground was hard. His only son John, who used to help him, was in prison.
The old man wrote a letter to his son and described his predicament.
Dear John, I am feeling pretty bad because it looks like I won't be able to plant my potato garden this year. I'm just getting too old to be digging up a garden plot. If you were here, all my troubles would be over I know you would dig the plot for me. Love,Dad
A few days later he received a letter from his son.
Dear Dad, For heaven's sake, don't dig up that garden! That's where I buried the BODIES! Love, John
At 4am the next morning, FBI agents and local police arrived and dug up the entire area without finding any bodies. They apologized to the old man and left. That same day the old man received another letter from his son.
Dear Dad, Go ahead and plant the potatoes now. That's the best I could do under the circumstances. Love, John