Sherlock's co-creator Steven Moffat has said that the fourth series of the show will be "an emotional upheaval".
Speaking to Entertainment Weekly he said: "[Season four] is going to be… I suppose you'd say… consequences. It's consequences. Chickens come to roost. It's dark in some ways - obviously it's great fun and a Sherlock Holmes romp and all that - but there's a sense of things coming back to bite you.
"It's going to be more of an emotional upheaval. Hopefully enjoyable and fun, all the things Sherlock must always be. It will be tough at times."
With regards to plot developments, Moffat said: "There are answers coming to questions which nobody has asked. There's one thing that no one has really brought up…"
