Co-creator Steven Moffat has now confirmed the special will take place in Victorian London, validating fan assumptions about the episode. Last month the show’s stars Benedict Cumberbatch and Martin Freeman were spotted filming Sherlock in 19th century clothes, causing fans to wonder if perhaps the crime-fighting duo attended a costume ball, or ir perhaps it was just some kind of dream sequence within the special. But no: The 90-minute episode literally takes place more than 100 years ago.

“The special is its own thing,” Moffat told EW before attending a panel at the South by Southwest conference on Monday. “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.”