Big things are afoot in the upcoming fourth season (or series, if you’re British) of Sherlock. After the trailer debut at this year’s Comic-Con, we were more than a little bit concerned for everyone’s favorite brainiac genius detective and his funny little uptight doctor pal. In their latest installment of the Benedict Cumberbatch and Martin Freeman-led series, things look gravely serious in a way they never have before—and based on our conversation with the cast, there’s no happy ending in sight. So while grilling the cast over on our Camp Conival stages, we were filled with dread, worry, and concern about our favorite characters. Could we get co-creators Mark Gatiss and Steven Moffat to spill the beans about Moriarty? What about producer Sue Vertue, or Mary Watson herself, actress Amanda Abbington? Is there a third Holmes brother? Will he be played by Tom Hiddleston? Well, you’re going to have to watch below to find out.

Of course, that’s not all we got out of the cast—we also wanted to talk about what it takes to put on such a thrilling series. After all, working in an oeuvre as impressive and beloved (and recreated!) as Sir Arthur Conan Doyle’s—except maybe that other show the producers work on, Doctor Who.

Are you looking forward to Sherlock‘s fourth installment? What do you think of their mysterious final words about season four? Have any thoughts or theories on Sherrinford? Let us know in the comments below!

Alicia Lutes is the Managing Editor of Nerdist and creator/co-host of Fangirling. Find her on Twitter (because she’s not trying to make you do any detective work).