Gummer, who can also be seen on "The Good Wife," will play a street-smart spy named Nora, "who is sent to the Hill as a liaison to Jim Meeks (Christopher Denham) and uses her charm and sexuality to pass atomic secrets to the Soviets." Gummer's recent screen credits include "Cake," "Echo Park" and "Emily Owens, M.D." She won a Theatre World Award for her performance in Noah Haidle's 2005 Off-Broadway play Mr. Marmalade, and earned a 2007 Lucille Lortel Award nomination for her performance in Theresa Rebeck's The Water's Edge. She made her Broadway debut in the 2008 revival of Les Liaisons Dangereuses.
The series, created and penned by Sam Shaw, features direction by Thomas Schlamme. The TV program follows the creation of the first atomic bomb and the scientists and their families based in Los Alamos. The series is not related to Woody Allen's film Manhattan.