The duke wants to know why the kid didn't die when he stabbed him in the head. He's worried that another kid will show up in the family after the death of zheng. The duke tells him that if he doesn't kill the kid now, he'll be a threat to his house. The kid is stealing the flower from the duke's house, and the duke won't be able to kill him. He tells the kid to go and kill the guy. The dude is only at the "transforming qi" stage, which means he's got the ability to beat people higher than his own level.