Summer Glau (; born July 24, 1981) is an American actress best known for her roles in science fiction and fantasy television series: as River Tam in Firefly (2002) and its continuation film Serenity (2005), as Tess Doerner in The 4400 (2005–2007), as Cameron in Terminator: The Sarah Connor Chronicles (2008–2009), and as Isabel Rochev / Ravager in Arrow (2013–2014).