After the so-so one-off special over Christmas, it's good to see Sherlock returning to normality - or at least as normal as Sherlock gets.

When last we left 'ol Shirley, he was about to sent off to Eastern Europe when, out of nowhere, Moriarty - seemingly from the dead - managed to commandeer each and every screen in the country with a somewhat terrifying message.

While this trailer doesn't exactly tell us a whole lot, there's a few glimpses of familiar faces. You can see Mary Marston, Mycroft Holmes, Lestrade and Mrs. Hudson, but we also see Toby Jones in an as-yet unspecified role.

Is Moriarty actually alive or is this just some scheme? What's going on with Mycroft? What's up with Toby Jones? Who exactly pays for Sherlock Holmes? Why doesn't Watson grow back his moustache?

So many questions, so few answers.