The Little help for Farmer Johnson

This is a story about Peter Johnson, a man who has a little potato farm.
He wasn't a rich man, but he always seems to harvest enough for his family. The family was able to work the land very well. When his son, Daniel, got old enough, he began working the farm too.
Dan grew up and did most of the heavy moving for his father, as he couldn't do as much.
One day, Dan drove to the city to get some supplies, he met his friend who he has not seen for some time. His friend asked if he could help him out and deliver a package for him, he said ok. He delivered the package, but didn't know a swat team was watching the house and was arrest with everyone. He was sent to prison for a year.
When spring came, he got a letter from his father that read, "Son, I was hoping that you will be out before planting season, but it looks like that I will have to plow the field myself.
The son, knowing his father would not be able to move the heavy equipment and knowing that the prison reads all letters before they go out; he wrote back, "Dad, please don't dig in the field, the mob had hidden their weapons in the field. 
About a week later the father wrote to his son. A swat team came to the farm and dug up the field where we plant. They said that the mob had hidden weapons in the ground. They dug up the whole field and didn't find any weapons or anything. They left the ground all broken up.
The son wrote back to his father, Dad, Now you can plant the potatoes.