The tv-show is based on the popular series of novels written by Sara Shepard.
The series follows the lives of four girls, Aria Montgomery (Lucy Hale), Spencer Hastings (Troian Bellisario),Hanna Marin(Ashley Benson) and Emily Fields(Shay Mitchell) after the disappearance of their friend Alison DiLaurentis(Sasha Pieterse). After one year Alison's body is found and the four girls begin reciving text messages from an anonymous source "A", who threatens to expose their secrets.
The first season has 22 episodes and the second season will premiere on 14 June 2011.
The theme song is performed by The Pierces and it's called "Secret".