"Sherlock" season 4 stars Benedict Cumberbatch and Martin Freeman offered the show's fans a treat last Thursday.

The pair were seen filming at the Gloucester Cathedral in full Victorian-era costume! What exactly will happen during the Emmy Award Winning show's Christmas special?

According to The Mirror, the Oscar nominee (who plays the legendary detective himself) exited the cathedral with his co-stars Freeman (who plays Sherlock's assistant and best friend, Dr. John Watson) and Abigail Abbington (who plays Mary Watson) in full costume to an audience of more than a hundred "Sherlock" fans.

The Mirror further reported that the crew were filming at the historic church's crypt.

"I don't know the plot but they moved a single bed into the crypt before they started filming," The news outlet quoted a church insider as saying.

"They also brought in some other props to put round the bed. I think they are pretending the crypt is another location and aren't using Gloucester Cathedral as part of the story."

Meanwhile, executive producer Mark Gatiss made some very special promises for the Christmas episode prior to the "Sherlock" season 14 official premiere in 2016.

Radio Times reported that the special will "completely" answer Jim Moriarty's mystery and whether or not he's alive or not.

As viewers of the BBC drama already know, Moriarty shot himself in front of Sherlock during season two to force him into killing his own self. However, he suddenly reappeared last season, most likely to play mind games with the sleuth detective.

Is he really alive or is it just another trick by Sherlock or his brother Mycroft?

When asked if Moriarty will keep appearing throughout season 4, Gatiss reportedly gave a vague answer to the publication, admitting that "it's very hard to put a lid on Andrew Scott..."

Tell us what you are the most excited to see in "Sherlock" season 4!