Summer Lyn Glau (born July 24, 1981) is an American actress and dancer, known for playing River Tam in the science fiction series Firefly and follow-up movie Serenity, and for playing Cameron in the series Terminator: The Sarah Connor Chronicles.Summer Lyn Glau (born July 24, 1981) is an American actress and dancer, known for playing River Tam in the science fiction series Firefly and follow-up movie Serenity, and for playing Cameron in the series Terminator: The Sarah Connor Chronicles.