“Something’s coming. Maybe it’s Moriarty, maybe it’s not. But something’s coming.” Comic-Con got a first look at Season 4 of Sherlock during today’s panel for the British mystery series. The trailer promises that “everything they know will be tested” and teases an intense, surprisingly action-heavy fourth season that seems closer to John le Carré than Arthur Conan Doyle. In the hall to discuss the upcoming season are star Benedict Cumberbatch, co-star Amanda Abbington, co-creators Mark Gatis and Steven Moffat  and producer Sue Vertue.

Benedict, Abbington and Gatis all agreed this morning that this season will be the darkest thing the showrunners have ever written for the show – “a real emotional roller coaster,” said Cumberbatch, but, Gatis added, “with jokes.” Whew.

Not shockingly, the subject of the show’s future came up during the fan Q&A. In a recent interview, Moffat said he would be “mildly surprised” if Season 4 is the last, the mildness due mainly to the busy schedules of stars Cumberbatch and Martin Freeman. A fan brought this up and prodded Cumberbatch to agree onstage to come back for Seasons 5, 6 and 7, and after some joking around, Gatis said, “We can exclusively reveal that there won’t be a fifth season … but there will be a sixth.”

More seriously, Moffat and Gatis clarified that they’ve never said Season 4 would be the last and that they didn’t mean to imply it, chalking it up to the imprecision of the interview process. Or, as Moffat put it, interviewiers “making it up.” However, they didn’t confirm a Season 5, so obviously the show has been cancelled. Just kidding!

In the end, the panel did manage to let slip what looks like a pretty big clue about the upcoming season. Asked by moderator Chris Hardwick to provide three key words about Season 4, Gatis and Moffat instead opted to provide three names: Thatcher, Smith and Sherrinford.

Fans of the original Holmes novels know that Sherrinford has particularly crucial importance. For one thing, it was the name Arthur Conan Doyle toyed with for his fictional detective before settling on Sherlock. For another, it was proposed by noted Sherlock Holmes scholar William S Baring-Gould and subsequently adopted by enthusiasts as the name of a hypothetical older Holmes brother. The idea being that the Holmes family, according to the original novels, were “country squires”, which means someone would have to be managing the family lands. With Sherlock and Mycroft both living in London, that job would have to go to someone else. It would seem that Sherlock will be incorporating that fan canon into the show in some form.

Gatis also said of the upcoming season the “things get resolved and there are evolving relationships.” Said Abbington: “I love playing Mary; she’s sassy, she’s ruthless. All the characters in Sherlock are flawed, making them compelling and great for all the cast to play.”

Have a look at the trailer above and tell us what you think.