The "Game of Thrones" prequel has found another lead.

"Poldark" star Josh Whitehouse is joining HBO's prequel pilot , just a day after the network announced the casting of Naomi Watts.

Whitehouse is best known for his role as Hugh Armitage on "Poldark" and will appear in the upcoming remake of "Valley Girl" opposite Nicolas Cage.

While Watts' character was described as "a charismatic socialite hiding a dark secret," details of Whitehouse's role remain unknown.

The prequel is set thousands of years before the events of "Game of Thrones," which will conclude with an eighth and final season next year on HBO. It chronicles the world's descent from the golden Age of Heroes into its darkest hour.

The official synopsis teases: "From the horrifying secrets of Westeros' history to the true origin of the White Walkers, the mysteries of the East to the Starks of legend — it's not the story we think we know."

HBO began developing a handful of "Game of Thrones" spinoffs last year, but only Jane Goldman's script (based on a story by herself and author George R.R. Martin) received a greenlight to make a pilot.

The pilot is likely to film early next year, though a director has yet to be hired.