Polly and The Doctor in “The Macra Terror”

Polly

The old shaft. Doctor, that's where Jamie is!

So they're going to pour this gas in the old shaft - gas they value above all else. What do you make of that, Polly?

Polly

For goodness sake, Doctor. What are you going on about?

Don't you see? Control are not pouring this poisonous gas into the old shaft to kill Jamie. They've quite another reason.