Davis was set to play Margot, a British national and the widow of a notorious terrorist. However, Davis had to exit the project last week over personal reasons, and Fairley will now take over the role.
Fairley is best known for playing Catelyn Stark on the HBO series. She also recurred on Suits last year as Ava Hessington.
24: Live Another Day will feature the return of Kiefer Sutherland as Jack Bauer, Mary Lynn Rajskub as Chloe and Kim Raver as Audrey. The limited series will also include new cast members such as Benjamin Bratt, Yvonne Strahovski, Tate Donovan, Gbenda Akinnagbe and Stephen Fry.
24: Live Another Day will bow Monday, May 5 on Fox.