Giving the Master an evil companion to match the Doctor’s good companions is an inspired idea, really pushing the idea of the two Time Lords being dark reflections of each other. And her clearly sexual (as far as anything can be clearly sexual in a family show) relationship with The Master-as-Harold Saxon mirrors the Doctor’s endlessly chaste relationships with his travelling companions.
Moen’s contribution? She’s managed to make a relatively small part compelling, and give a character who is excited at the idea of the rapid slaughter of 10% of Earth’s population a staggering credibility, in the circumstances. Davies has used the character as a powerful tool to underline the horrific nature of what’s happening, which has proved necessary with John Simm’s so-far-over-the-top-he’s-likeable portrayal of the Master. She gives a human edge to his alien villainy that brings it all so much closer to home.
So far we’ve seen her as the stereotype politician’s wife, with sensible hair, and buttoned-down outfit. From the looks of the picture, we’ll see her as a much more typical villain at the weekend.
Dramas like Doctor Who often stand or fall on their guest cast. So far, Moen’s Lucy Saxon has been one of the best.