Sara, played by Mira Sorvino, is a character who appears in the fourth season of the TV series "Falling Skies." She is a scientist who previously worked with the Espheni, the alien race that invaded Earth, and helped them develop a weapon that can wipe out the human resistance. However, Sara defects from the Espheni after realizing the true nature of their plan and becomes an ally to Tom Mason and the human survivors.

Sara is a brilliant scientist and has an extensive knowledge of the Espheni technology. She uses her skills to help Tom Mason and his team in their fight against the aliens. Despite her past with the Espheni, Sara is deeply committed to the human cause and will do anything to ensure their survival.

Throughout her arc on the show, Sara develops a strong relationship with Tom Mason, and the two share a romantic connection. However, their relationship is complicated by Sara's past and her uncertain loyalties. Despite this, she remains a vital member of the human resistance and plays a key role in their efforts to defeat the Espheni.

Overall, Sara is a complex and multi-layered character in "Falling Skies." Mira Sorvino's performance was praised for its nuance and depth, and she brought a compelling energy to the show's ensemble cast.