who is the person sending messages in pretty little liars
List of Pretty Little Liars characters "A" is the main antagonist of the series. "A" is stalking and torturing the Liars in relentless and creative ways and also threatens their friends and family. In the second season finale, it is revealed that Mona is "A". She is also the "A" who stalked Alison before her disappearance. However, when she is sent to Radley sanitarium, she is visited by CeCe Drake, who offers her a partnership and takes over the team of "A's", known as the A-Team.