Pretty Little Liars is a popular American teen drama mystery-thriller television series that aired from 2010 to 2017. Created by I. Marlene King, the show is based on the novel series of the same name written by Sara Shepard. The series follows the lives of four high school friends, Aria Montgomery (Lucy Hale), Spencer Hastings (Troian Bellisario), Hanna Marin (Ashley Benson), and Emily Fields (Shay Mitchell), who are reunited one year after the disappearance and presumed death of their friend Alison DiLaurentis (Sasha Pieterse).