'Sherlock' Season 4 Air Date, Characters & Trailer: Filming Starts April -- Everything We Know So Far [Plot & Rumor Round Up]

"Sherlock" Season 4 is among the most-anticipated TV series in BBC. Many fans are looking forward to its return to witness the next adventure of the consulting detective Sherlock Holmes (Benedict Cumberbatch) in the modern day London.

According to Morning Ledger, "Sherlock" Season 4 is set to start filming April this year. Per the report, all the mains stars will be reprising their roles so expect to see more of Amanda Abbington as Mary Watson, Louise Brealey as Molly Hooper and Jonathan Aris as Anderson.

After the success of its holiday special episode, BBC confirmed that Cumberbatch will return in an all-new "Sherlock" Season 4, Master Herald reported. At the time, fans are still not over season 3, where it was hinted that Sherlock might have another brother after Mycrof said, "You know what happened to the other one."

There are rumors that the detective's third brother will be played by Tom Hiddleston. The actor was popular in his evil role of being the Norse God of Fire and "Thor's" trickster brother, Loki.

Hiddleston's potential involvement in "Sherlock" Season 4 is something fans are looking forward to seeing. They are excited if his character will be causing chaos in the show too, just as what he always does in "Thor."

Aside from a potential new character, many are wondering how "Sherlock" Season 4 is different from the first three seasons. The writer-producer Steven Moffat was asked with this question on his interview with Entertainment Weekly, and he hinted some revelations.

Moffat stressed that the first series was about the beginning of a friendship. The second was about the formative stages, the love, fear and loss. The third was about the good days.

He noted that Sherlock Holmes has a lot of humor but this is missing in the adaptations, he hinted that in Season 4, the audience would get to experience the fun and fright at the same time.

"There's a lot of humor in Sherlock Holmes, and it's ignored in a lot of adaptations. [Season 4] is going to be... I suppose you'd say... consequences," he said. "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 not a safe, sensible way to live. It's hilarious and exhilarating some days, but some days it's going to be bloody frightening."

Crossmap speculates that things might turn sour among Sherlock, Dr. John Watson and his wife Mary. There are rumors that Mary will die because the two had a short-lived marriage. Morgan Freeman confirmed that Mary dies but Mark Gatiss countered saying that what's written in the stories might not happen in the series.