Mark Gatiss, co-creator of 'Sherlock' which is the contemporary version of Sir Arthur Conan Doyle's detective stories that air BBC America, recently disclosed that fans should be prepared for an "unexpected tragedy" when the series returns for its Season 4 in late 2015 or early 2016.

This has led fans speculating about which character will meet his/her end in the upcoming season.

During a recent interview with Radio Times, Gatiss said, "You can always expect tragedy as well as adventure, that's just how it goes," replying to a query about what 'Sherlock' Season 4 has in store for them.

While these were simple words from Gatiss, the Christian Post says that they made all concerned wonder as to which character will be facing the axe in the new season of the show. They think so because there is no chance of either Sherlock Holmes (Benedict Cumberbatch) or John Watson (Martin Freeman) being eliminated. Therefore, fans are wondering whether it will be John's wife Mary Watson (Amanda Abbington) who will be killed.

In fact, Freeman, whose real life partner portrays the character of Mary, had, in the past, teased about Mary's death.

Earlier this year, Freeman had told The Telegraph, "While we play fast and loose with the original stories, we generally follow the trajectory of what Conan Doyle did. So [John] gets married, and then Mary dies - so at some point presumably she'll die."

Mary's death in 'Sherlock' Season 4 is only possible provided Gatiss and the other co-creator Stefen Moffat opt to pursue the original story by Sir Arthur Conan Doyle. However, Gatiss has asked the audience not to make any speculations on the basis of the original story 'Sherlock Homes'.

Explaining further, Gatiss said, "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. It should be clear by now that while... 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."

Due to the very busy schedules of the stars of 'Sherlock', the filming of Season 4 will commence by the end of 2015 and the show will be released either in late 2015 or early 2016, but the producers will air a special installment sometime in January 2015 to reunite Holmes and Watson.