We definitely haven't seen the last of Andrew Scott's Moriarty on Sherlock.

At least, that's what co-creator Mark Gatiss was teasing when he spoke with MTV News - but don't expect to see the full picture any time soon.

"There's a master plan," he said. "There's a plan. There is a long-term plan - very long-term."

Although Moriarty killed himself in 2012's 'The Reichenbach Fall', his presence remains heavily felt in the show.

Meanwhile, Gatiss talked about the upcoming Victorian special 'The Abominable Bride' and how the writers approached the female characters.

Hartswood/Robert Viglasky

"It wasn't a [challenge] really with Holmes and Watson for this one, because they were very much modern men then," he said. "The big challenge was the role of women.

"You can't ignore how it was - in fact, it's fundamental to the plot. It was very interesting. A lot of things you would just take for granted in terms of how women got about - in that society - are totally different."

A fourth full series of Sherlock consisting of three episodes will begin filming in 2016.

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