Tonight’s “World Enough and Time” is the last episode before next week’s season finale, which will be the last episode before this year’s Christmas special – which will mark, somehow, the final appearance of Peter Capaldi as the current incarnation of the Doctor. The show’s current plot line, therefore, is running out of time – and tonight, Time is in play not only as an abstract, but as an adversary. And so is another Time Lord, making a return, and significant, appearance. Also making a return appearance tonight: one of this show’s original villains back when it premiered in the 1960s, the Cybermen!