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