In a land, there is a local custom that the patriarch in the family is killed after his son’s marriage, as he is considered the useless. However, a young man hides his father instead of killing him after his marriage. Later, an unknown animal comes to the destroy the food at the local king's warehouse. The boy's father asks his son to use a cat to see if it is a mouse, and the son finds that it is, indeed, a mouse. Later, the son uses turquoise as his father had told him to distinguish a mare from a female mule. Under the guidance of his father, the son becomes more and more intelligent and capable. Since then, people understand the value of old men, and the custom was abandoned.