The much-awaited fourth season of BBC's "Sherlock" is still over a year away, but fans of the series can still have their fill of the iconic detective's adventures when the show's Christmas special airs during the holidays this year. 

Still, little has been revealed about the plot for "Sherlock" season 4. In order to find out more, thousands of Sherlock fans flocked to Hall H of the San Diego Convention Center on July 9 to attend the panel appearance of the cast of "Sherlock" at this year's San Diego Comic-Con.  

During the panel, series creator Steven Moffat revealed that the fourth season of the show will have a darker twist. 

"We've got a clear idea of what we're going to do and it's going to be a clear shift in tone," Moffat said.

But whatever that "dark stuff" is, the series creator said that there will still be a lot of jokes, interesting espionage activities, as well as other fun stuff. 

"It's dark in some ways – obviously it's great fun and a Sherlock Holmes romp and all that – but there's a sense of things coming back to bite you," the series creator added. 

But while Moffat admitted that the scripts for the three-episode season are still not done, he announced that they will release a special one-hour episode in select theaters and TVs soon. According to the series creator, the special stand-alone episode will be set in the same time frame as the original time of Sir Arthur Conan Doyle, the writer of the original "Sherlock" detective stories. Moffat also stated that they faced several challenges while writing that particular episode since they have to adapt the style of the original "Sherlock" novels, where women did not have a lot of speaking lines. 

The release date for the stand-alone episode of "Sherlock" is still unannounced.