In line with the upcoming "Sherlock" season 4, "Thor" actor Tom Hiddleston has been revealed to join the series as Sherlock's brother while the story plot is teased to be more ominous.

According to Unreality TV UK, Hiddleston is set to join "Doctor Strange" actor Benedict Cumberbatch and show creator Mark Gatiss in "Sherlock" season 4. Sources told the publication that the "Thor" and "Crimson Peak" actor is set to play the role of Sherrinford Holmes, which has reportedly led to "massive excitement" among fans.

Previously, Gatiss revealed that he would love to have Hiddleston in the show, though he pointed out that it the actor's hectic filming schedule had a conflict with the series' filming timeline. However, recently, the show creator revealed that he would be more that eager to land the actor for a role in the new series.

Hiddleston is assumed to be promising in his character portrayals in films with dark toned storyline. The actor is known for his roles as Loki in Joss Whedon's "The Avengers," Kenneth Branagh's "Thor," and Alan Taylor's "Thor: The Dark World," and Thomas Sharpe in Guillermo del Toro's "Crimson Peak." He is set to reprise his role as Thor's adversary in Taika Waititi's "Thor: Ragnarok" and Jordan Vogt-Roberts' "Kong: Skull Island."

According to IB Times, the core subject of "Sherlock" season 4 is set to be how women were treated in the Victorian era. As per Gatiss, there was a bit where the men were about to go off on an adventure and Mary was not allowed to join them.

BBC producer Steven Moffat said that season 4 would be darker and they were going to try to take it somewhere they had never seen before, as per Crossmap. He joked that he did not mean outer space, but it would be a challenging place to go, which builds to a darker climax.

"Sherlock" season 4 is set to commence its filming in spring and is assumed to premiere in January 2017.