"Game of Thrones" actress Natalie Dormer joining "Elementary"

One of the women of "Game of Thrones" is heading to "Elementary."

Natalie Dormer has been cast in a pivotal role on CBS' Sherlock Holmes drama, the network announced Tuesday.

Dormer will play Holmes' former lover, Irene Adler, in a three-episode arc on the show. She was Holmes' first and only love in London, and her mysterious murder at the hands of Moriarty caused his downward spiral into drug addiction.

"We're moving to the next chapter in our show -- and in some ways, to a previous chapter in Holmes' story," said executive producer and creator Rob Doherty. "Irene Adler is perhaps the most pivotal relationship in Sherlock's life, and I can't think of an actress better suited to the challenge than Natalie."

Dormer plays Margaery Tyrell on HBO's "Game of Thrones" and also starred as Anne Boleyn on Showtime's "The Tudors." Her film credits include "Captain America: The First Avenger" and the upcoming movies "The Counselor" and "Rush."

"Elementary," which airs Thursdays at 10 p.m. ET, stars Jonny Lee Miller as a modern-day Sherlock Holmes and Lucy Liu as Dr. Joan Watson. The show's two-hour season finale begins May 9.