Sarah Clarke Sarah Clarke

It's a Covert Affairs switcheroo!

24 star Sarah Clarke has replaced Rebecca Creskoff (Hung) as a new mentor for Annie (Piper Perabo) on the USA drama, has learned exclusively.

Covert Affairs bosses on "bittersweet" finale and what's next for Annie and Auggie

As we reported last month

, Creskoff was cast to play Lena Smith in Season 3, but she has now dropped out due to a scheduling conflict. Production is currently underway on the season premiere, but Creskoff had not yet shot any scenes.Clarke will now play Lena, a legendary CIA operative running her own division who will become an important figure in Annie's career. But there may be more to Lena than meets the eye.

Covert Affairs exclusive: Meet Annie's new assignment — a KGB spy!

Clarke played Nina Meyers on 24 for three seasons and has most recently played Renee, Bella's mom, in the Twilight film series. Her other TV credits include House, Life and Men of a Certain Age.Season 3 of Covert Affairs will premiere this summer on USA. Clarke, who will recur throughout the season, will make her debut in the first episode.