The Oscar winner will play Sara, a woman far removed from her former life as a graphic designer. In the years since the alien invasion, she's now dogged by death at every turn. When she comes across John Pope (Colin Cunningham), the fearless fighter joins the resistance and develops a strong personal bond with him.
Sorvino, whose TV credits include House and Will & Grace, is well-known for her roles in Romy and Michele's High School Reunion and Woody Allen's Mighty Aphrodite, for which she won a Best Supporting Actress Oscar.
The fourth season of Falling Skies will return next summer.