Amy Louise Acker (born December 5, 1976) is an American actress, best known for her roles as Root on the scifi drama series Person of Interest (2012–2016), Caitlin Strucker on the superhero drama series The Gifted (2017-2019, based on Marvel Comics' X-Men), Winifred Burkle / Illyria on the supernatural drama series Angel (2001–2004), and Kelly Peyton on the action drama series Alias (2005–2006).