Sherlock co-creator Steven Moffat has confirmed the 2015 special will take place in Victorian London.

“The special is its own thing,” Moffat told EW. “We wouldn’t have done the story we’re doing, and the way we’re doing it, if we didn’t have this special. It’s not part of the run of three episodes. So we had this to do it – as we could hardly conceal – it’s Victorian. [Co-creator Mark Gatiss] and me, we wanted to do this, but it had to be a special, it had to be separate entity on its own. It’s kind of in its own little bubble.”

The special is pretty much finished, Moffat added, and he’s very pleased with the result. No air date is set, but the special is widely expected to air in the UK around December.