"Sherlock" co-creator Mark Gatiss had dropped a bomb on the show's fans by saying that there will be an "unexpected tragedy" to befall the show when it returns for its fourth season. This got fans speculating and wondering which character will meet his or her demise. 

"You can always expect tragedy as well as adventure, that's just how it goes," Gatiss told Radio Times during an interview, in response to a question about what is to be expected from the upcoming season. 

Those few words got everyone wondering who will be axed because Sherlock Holmes (Benedict Cumberbatch) and John Watson (Martin Freeman) will definitely be safe. Hence, fans are speculating that it will be John's wife Mary Watson. Mary is played by Freeman's real-life partner Amanda Abbington. 

In the past, Freeman already teased about Mary perishing. 

"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," Freeman told The Telegraph early this year. 

However, this storyline will only happen if Gatiss and co-creator Stefen Moffat choose to follow the original "Sherlock Holmes" story by acclaimed writer Sir Arthur Conan Doyle. On the other hand, Gatiss said that the audience shouldn't make assumptions based on the original story. 

"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," Gatiss said. 

Due to the very busy schedules of the stars of "Sherlock," the new episodes of the TV series will be aired either late 2015 or early 2016. Season 4 production will happen by the end of 2015, but there will be a special installment airing to reunite Holmes and Watson. It will be filmed in January 2015.