Ace and The Doctor in “The Last Day Part Two”

Ace

The Dark Citizens were all about potential. They could see the path we all take through life. The Web of Time. All those different decisions, all those roads not taken… I think that they knew something most of us don't like to admit.

Which is?

Ace

That most of us will always end up the same, whatever we do! There'll be gradations, of course; nurture affects nature every day. But someone who was -- for example -- a really manipulative and controlling person… well, they'll always become something dark.

Mmm… Maybe you're right.

Ace

So it's all about stopping them before they go too far.

Perhaps…