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). As of 2017, she stars as Caitlin Strucker on the superhero drama series The Gifted, based on Marvel Comics’ X-Men.
Acker made her major television debut when she starred as Winifred “Fred” Burkle in Angel (seasons 2–5), and also as the character of Illyria for part of the show’s fifth and final season. She won the 2003 Saturn Award for Best Supporting Actress on Television for her portrayal.
She joined the cast of Alias in 2005 for its final season, playing villainess Kelly Peyton. Acker graduated from guest star to fully credited cast member as the show entered the final episodes in April and May 2006. Also in 2005, Acker provided voice acting for the character of Huntress on the animated series Justice League Unlimited. She went on to make a guest appearance on How I Met Your Mother, in which she was reunited with Angel co-star, Alexis Denisof (the real-life husband of HIMYM star Alyson Hannigan), who had a recurring role on the show.
In 2010, she was a series regular in the ABC drama Happy Town, portraying the character Rachel Conroy. That same year, she starred in the season-one finale of the Fox series Human Target, as the mysterious Katherine Walters. On May 25, 2010, she appeared on CBS’s The Good Wife. She appeared in the horror movie The Cabin in the Woods, released April 13, 2012. In 2012, she made guest performances in Warehouse 13, Once Upon A Time, and Grimm. In 2012, she starred as Beatrice in Joss Whedon’s Much Ado About Nothing.