The 'Sherlock' Christmas special is a "proper gothic horror".
Benedict Cumberbatch
The BBC series - which stars Benedict Cumberbatch and Martin Freeman - will air a Victorian special, 'The Abominable Bride', over the holiday season and actress Amanda Abbington insists fans are in for a festive fright.
She said: "It's a proper gothic horror, it's properly scary edge of your seat and it takes it back to the original."
Writer and actor Mark Gatiss added to Digital Spy: " It's a Christmas ghost story, a Christmas treat."
Producer Steven Moffat, who created the BBC series with Mark, insisted that this storyline is a standalone and would not have been included in the show if they weren't making a Christmas special.
He said: " We wouldn't have done it unless we had the special, this is over and above our normal 'Sherlock'. We do three episodes at a time and we didn't want one of those three to be a sidestep so this was the perfect time."
While season four is underway, with both Steven and Mark writing episodes, Steven admitted he is slightly behind as he got caught up with his other show 'Doctor Who'.
He explained: "Mark's further ahead than me because I got caught up in 'Doctor Who' Christmas. But we're underway, that's the day job right now."
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