DOCTOR: I was once a man with a masterplan. I’d seek out injustices, topple governments, all in the name of the greater good. I’d started doing the maths, you see…. This is how evil starts, with the belief that the ends justify the means. But once you start down that road, there’s no turning back. What if you can save a million lives, but you have to let ten people die, or a hundred, or a hundred thousand. Where do you stop?