Ambrose will play Jilly Kitzinger, a sharp press agent dealing with a very important client.
The actress, known for her role on the HBO series "Six Feet Under," has appeared on Broadway in Exit the King and Awake and Sing!, as well as in the Public Theater productions of Romeo and Juliet and Hamlet.
"Torchwood," which stars John Barrowman, will premiere its new season in July on Starz.