What is the Matter, Dad?

It is six o'clock in the evening. Nelly's father has just come home from work. Now he wants to have a bath. He takes his hairbrush and goes to the bathroom. But he cannot get into the bathroom. The door is shut. He hears Nelly talking in the bathroom.
“Nelly,” asks the father, “who are you talking to?” Nelly does not answer. She opens the door of the bathroom. The father sees his daughter and the cat then.
The girl says to the cat, “You have had a hot bath and now you must dry yourself with the towel. You see, Father has brought us a hairbrush. He is going to help me...”
The father calls the mother. The mother comes into the bathroom and says, “Have you already finished, Nelly? Why? That's your father’s towel! Now stop that and let the cat go.”
The girl puts the cat on the floor and says, “Why, Mum? Puss and I swept the floor in the hall. So we have just had a bath. What is the matter, Dad? After a bath I usually dry my cat with this towel.”
The mother and father look at each other. They do not know what to say. The cat is wet and it runs away. Nelly is a good girl, but she does not understand. She loves her cat very much.