Aunt Marge: You mustn't blame yourself about how this one turned out, Vernon. It's all to do with blood. Bad blood will out. What is it the boy's father did, Petunia?
Aunt Petunia: Nothing. He didn't work. He was unemployed.
Aunt Marge: And a drunk too, no doubt?
Harry: That's a lie.
Aunt Marge: What did you say?
Harry: My dad wasn't a drunk!
Aunt Marge: Don't worry. Don't fuss, Petunia. I have a very firm grip.
Harry, angered by Aunt Marge's accusations, causes the glass in her hand to shatters, startling everyone at the table.