It's a potential spoiler for the next series. Do you still not mind hearing it?

As for the multi-series thing, well, they never really faced whoever was behind the voice/"Silence will fall", did they? I mean, whoever it was was a key player, but they took a back seat to the rest of the action. So in a way, it's a bit like a comic book where the hero has just fought off a lesser villain, only to find that there was a bigger one pulling the strings. I actually love that sort of story, provided they don't just keep replacing every villain with a bigger one each series.