A new villain is set to join the cast of "Sherlock" season 4, and he is none other than Culverton Smith.

One of the most prominent Doyle villains, Smith will be played by actor Toby Jones. His character is from "The Adventure of the Dying Detective" and is believed as the one responsible for the death of Sherlock Holmes' nephew.

According to Jones, Smith is a tropical disease expert who once sent a disease-infected pin to Sherlock's Baker Street to kill the notable detective. Suspecting a foul play, Sherlock pretended to be ill in order to trap the villain and have him arrested. So as to make sure that his trick would work, Sherlock tested the ploy on his good friend Doctor Watson.

Jones revealed that his character will debut in episode 2 of "Sherlock" season 4, which is currently being filmed.

Aside from Jones, two more actors are joining the cast of the series. The first is comedy actor James Holmes, who will appear in the premiere episode as a character referred to as "Passenger." The other one is "Dr. Who" star Daniel Hoffmann-Gill, whose role in the upcoming season has not been fully disclosed yet.

The regulars from the previous seasons are reportedly reprising their roles in the next installment.

In other news, Mark Gatiss and Steven Moffat recently revealed that the focus of the upcoming series will be "the climax of the story we've been telling from the beginning." Moffat added that season 4 will be so good that fans will be desperate for a 5^th season.

"Sherlock" is expected to return in January 2017.