Ireland will play Pauline, wife of Frank, who will be played by Tony winner Christian Borle. The couple's story follows them seeking help from Masters in conceiving a child.
William Masters and Virginia Johnson are played by Michael Sheen and Lizzy Caplan. The two are portrayed as pioneers of human sexuality whose research inspired the sexual revolution.
"Masters of Sex" also stars Caitlin Fitzgerald, Teddy Sears and Annaleigh Ashford.
The second season premieres July 13. Visit sho.com/sho/masters-of-sex/home for more information.