The highly anticipated fourth season of Sherlock is set to feature a healthy dose of tragedy, as noted by one of the show's executive producers.

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Sherlock executive producer Mark Gatiss spoke with RadioTimes.com recently about the fourth season, which is set to air in 2016. He previewed that the series will mix tragedy with the usual exciting crime solving.

"You can always expect tragedy as well as adventure, that's just how it goes," he said.

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As the report speculates, this tragedy could include the death of John Watson's (Martin Freeman) wife Mary (Amanda Abbington), which takes place in the Arthur Conan Doyle books on which the series is based.

However, it is possible that the series will diverge from certain elements of the books.

"Just because it's in the stories doesn't mean it'll happen in the series because there's an awful lot of changes and an awful lot of places to go and things to do," Gatiss teased.

Gatiss listed an example of the series changing course from the Sherlock Holmes stories:

"It should be clear by now that while, of course, Doyle is our absolute god, we have gone quite a long way away as well - we've introduced Sherlock and Mycroft's parents [for instance], I don't think they've ever been seen in any adaptation - so there are lots of surprises to come."

As of now, Sherlock is expected to return in December 2015 for a Christmas special, while the fourth season is set to begin airing in early 2016.

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