DOCTOR: My dear girl, the one purpose in growing old is to accumulate knowledge and wisdom, and to help other people.

SUSAN: So I’m to be treated like a silly little child.

DOCTOR: If you behave like one, yes.

SUSAN: Oh, look, Grandfather. I understand the Sensorites. They’re timid little people. Because their minds and mine can communicate sometimes, they trust me.

DOCTOR: Yes, and I assure you we shall make good use of that fact, but not without discussions. You will not make decisions on your own accord. Now, do you understand? Is that quite clear? Well, is it?

SUSAN: Look, I’m not saying I’m as clever as you, of course I’m not. But I won’t be pushed aside. I’m not a child anymore, Grandfather. I’m not.

DOCTOR: Oh, Susan, Susan.