The series follows the lives of Aria Montgomery (Lucy Hale), Spencer Hastings (Troian Bellisario), Hanna Marin (Ashley Benson) and Emily Fields (Shay Mitchell), four girls whose clique falls apart after the disappearance of their queen bee, Alison DiLaurentis (Sasha Pieterse).
One year later, they begin receiving messages from a mysterious figure using the name "A" who threatens to expose their secrets. At first they think it's Alison herself, but after she is found dead, the girls realize that someone else knows their secrets -- including long-hidden ones they thought only Alison knew.
Aria and her family return from Iceland, moving back into their old house in Rosewood, Pennsylvania. She, Hanna, Spencer, and Emily have grown apart since Alison's disappearance. She meets college graduate, Ezra Fitz. She later finds that after all her time in Iceland, formerly overweight Hanna is now thin, glamorous, and best friends with former nerdy outcast, Mona Vanderwaal.
When she begins school she finds that Ezra is also her new AP English teacher. Aria later begins to receive texts and emails from an unknown source that reveals secrets that only Alison knew and more recent ones, including Byron's affair with Meredith and Aria's with Ezra, signed, "A".
When Alison's body is discovered under a block of cement, she, along with the other three girls, receive a text at the same time, "I'm still here b**ches, and I know everything." Signed, "A".
Spencer Hastings (Troian Bellisario) is the "preppy girl" of the group who strives to be perfect all round because she lives with her family's expectations looming over her head. Hanna Marin (Ashley Benson) is the "it girl" of the group and has taken Alison's place as the most popular girl at Rosewood in Alison's absence.
Previously chubby, Hanna became slimmer after Alison's disappearance, and now shoplifts. Rejected by her boyfriend, a distraught Hanna crashes his car into a tree, later working at a burn clinic to pay off her debt. She continues to be harassed by "A", but stays together with the her friends to get through it Emily Fields (Shay Mitchell) is a competitive swimmer and the "jock" of the four.
She befriends Maya St. Germain, the new resident of Alison's former home, and the girls grow closer. Alison DiLaurentis (Sasha Pieterse) was the former leader of Rosewood's premiere clique. Ruling the group with an iron fist, the vicious but charismatic Alison had gone missing during a slumber party. Even after a year, her disappearance was still unsolved. When Aria, Hanna, Spencer, and Emily begin receiving threatening messages from "A" reminding them of their darkest secrets, they suspect that "A" is Alison, in whom they had all confided. But, Alison's body is soon discovered buried in her former backyard. i love Pretty little liars!!!!! :DDD