In my view, the second episode of this season is much better than the first. My major issue with the first episode was that getting rid of Prisoner Zero had an irritating deus ex machina solution involving the Doctor doing some Clever Science and somehow Fixing Everything, a shortcut for good story-writing that I hoped would go out with Russell T Davies. I won’t spoil it for you, but in the second episode, the solution was contained very neatly in the problem. I found that much more satisfying.

Also, the second episode was genuinely, satisfyingly scary. And the Doctor gets even more interesting and complicated. :) I hope this series keeps getting better.