"A", is the anonymous main antagonist of the Pretty Little Liars series. "A" is an anonymous character who sends threatening messages to Alison DiLaurentis, Aria Montgomery, Spencer Hastings, Hanna Marin, Emily Fields, and since recently, Mona Vanderwaal. "A," who was previously believed to be one character, is revealed to be more than one person in the Season 2 finale: the "A-Team." Mona was revealed to be the first "A" in "UnmAsked." Her motives were that the Liars "took" Hanna away from her. She gets into a struggle with Spencer, and ends up being sent to Radley for treatment. She is released several months later.
It is revealed that Mona isn't the only "A," and that there are multiple people on this team working together, including a leader. Toby Cavanaugh, Spencer Hastings's boyfriend, was revealed to be the second "A" in the mid-Season 3 finale. However, it has been revealed that Toby's intentions were to protect Spencer.
Mona Vanderwaal was the leader of the "A-Team" until UnmAsked, when an anonymous person in a Red Coat took her place, and dropped Mona down to a lower ranking. It is implied and confirmed by Marlene King that Mona was the "A" tormenting Alison before her disappearance.
Since "A DAngerous GAme," Toby, Mona and Spencer are kicked off of the "A-Team."
It's revealed in "Now You See Me, Now You Don't," that CeCe Drake is the evil Red Coat.
- Villains Wiki