Finally, after years of waiting, “Sherlock”season four began filming.

Actor Mark Gatiss confirmed the start date of the filming. He told Magic FM that the new series is expected to arrive on BBC One in early 2017 and that its flavour would be “bittersweet,” Denofgeek reported.

“Bittersweet. It’s always bittersweet,” said Gatiss, who recently accepted an award for Best Supporting Actor at the London theatre Oliviers.

Actress Amanda Abbington, who plays the role of Mary Watson,also confirmed the news on Twitter, Newseveryday reported.

“Sherlock” showrunner Steven Moffat earlier confirmed that season four of the TV adaptation of Sir Arthur Conan Doyle novel is set to start filming in April 2016. “I think we’re shooting next year, April-ish,” he said.

However, Denofgeek noted that it remain uncertain whether the first three episodes of the upcoming season will be filmed in an uninterrupted block, or if production will be halted between episodes to adopt to the busy schedules of lead stars Benedict Cumberbatch and Martin Freeman.

Cumberbatch is busy for his Marvel movie, “Doctor Strange.” Freeman, on the other hand, also got himself occupied with a role in “Captain America: Civil War,” but he was certain to return as Sherlock’s friend and confidante, Dr. John Watson.

Meanwhile, Deanofgeek cited Moffat’s interview with Entertainment Weekly where he provided a few teases, including the guarantee that series four would contain answers “to questions which nobody has asked.”

“We’re very exultant about a little thing we’ve set up that no one is talking about,” said Moffat.

When asked what would be the theme of the fourth season, Moffat said: “It’s consequences. Chickens come home 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 not a safe, sensible way to live. It’s hilarious and exhilarating some days, but some days it’s going to be bloody frightening.”

“Sherlock” season four is expected to premiere early in 2017 on BBC.