ZOE: How do you know the next section to this one is an opposite pole?

DOCTOR: Well I don't, Zoe.

ZOE: Well, if it's similar, your idea won't work, will it? We'll just shoot off in the opposite direction.

DOCTOR: Zoe, don't be such a pessimist.

JAMIE: It's not an audio lock, is it?

DOCTOR: No, Jamie, it isn't.

JAMIE: Ah, that's a relief.

DOCTOR: Jamie, I think you don't appreciate all I do for you.