•  Benedict Cumberbatch and Martin Freeman attend a screening of the Sherlock 2016 Christmas Special at Ham Yard Hotel on December 19, 2016 in London, England.

Benedict Cumberbatch and Martin Freeman attend a screening of the Sherlock 2016 Christmas Special at Ham Yard Hotel on December 19, 2016 in London, England. (Photo : Getty Images/ Jeff Spicer)

"Sherlock Holmes" Season 4 premiere titled "The Six Thatchers" killed one important character, Mary Watson (Amanda Abbington). "Sherlock Holmes" big boss Steven Moffat explained that her demise was needed in order to refocus on the story of of Sherlock Holmes (Benedict Cumberbatch) and John Watson (Martin Freeman).

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[THIS POST CONTAINS SPOILERS OF "SHERLOCK HOLMES" SEASON 4]

Everyone was left shocked by Mary's death when "Sherlock Holmes" Season 4 returned, but Moffat revealed that "Sherlock Holmes" would always come back to its original storyline. He added that the English detective drama series was reset to the old version and the most traditional format of the show.

"The reality of this, of course, is that Sherlock Holmes is about Sherlock and Dr. Watson and it's always going to come back to that - always always always," Moffat told Entertainment Weekly. They had fun making it a trio, but it doesn't work long term. Mary was always going to go and we were always going to get back to the two blokes.

With Mary's death, Sherlock and John's friendship would be strained because she died from taking the bullet that was supposedly for Sherlock. When asked how the storyline would reset to the old format with Sherlock and John's rift, Moffat reassured that will be tackled in the next episodes of "Sherlock Holmes" Season 4.

When it comes to the old cast, Moffat reiterated that everything could happen, and no one is secured except for the detective duo. He promised a more emotionally charged episode with a mixture of laughter when Season 4 returns.

Meanwhile, Freeman separated from Abbington in March 2016, his real partner of 16 years. In an interview with The Observer as cited by Telegraph, he admitted that working with her until "Sherlock Holmes" Season 4 episode 1 was "odd" due to their real status.

The English actor, who played Tim Canterbury in "The Office," admitted that he and Abbington remained good friends, while adding that working with her was interesting because they know each other very well. In the previous interviews, Abbington revealed that his busy career when he filmed "The Hobbit" and "Fargo" abroad has something to do with their separation.

There will be no Freeman and Abbington anymore in the upcoming episodes of "Sherlock Holmes" Season 4, but the two assured that they separated amicably. He can also visit his kids anytime in their old home.

When the Season 4 premiere ended, a parcel was received by Sherlock. A DVD came from Mary instructing him to save John. The teaser also revealed that John is exchanging text messages with a woman he met on a bus.

The flirty encounter of John and the unidentified woman may indicate a looming affair right after Mary's death. Everything will be revealed in the upcoming episode of "Sherlock Holmes" Season 4. Watch the teaser for episode 2 titled "The Lying Detective" here: