Season One (Rumours)

The first season of Pretty Little Liars, based on the books of the same name by Sara Shepard, premiered on June 8, 2010 and concluded on March 21, 2011 on ABC Family.

The show premiered to 2.47 million viewers and retained a regular audience of 2.5 million viewers during its summer run. The summer finale scored 3.07 million viewers, achieving a series high. The show went on hiatus and returned with its winter premiere on January 3, 2011, with 4.20 million viewers, becoming one of ABC Family's top telecasts to date.

Overview
Best friends Aria Montgomery, Emily Fields, Hanna Marin, and Spencer Hastings grow apart when their clique leader and 'queen bee' Alison DiLaurentis goes missing. A year later they all begin receiving messages from the mysterious "A" who threatens to reveal their darkest secrets. Aria has just returned from Iceland after a year or so with her family and still feels unable to forgive her father who cheated on her mother, who's still unaware of it; she also discovers that her new English teacher (Ezra Fitz) is the same guy she met and made out with at a bar the day before. Hanna is now the "it" girl of the school, along with former geek Mona Vanderwaal. Both girls indulge in shoplifting; later, Hanna gets in trouble, forcing her mother to sleep with a detective for her release. Spencer has feelings for her sister's fiancé (Wren Kingston). Emily befriends a girl named Maya St. Germain, who's just moved into Alison's old house. Later, Alison's body is found buried in her old backyard.

Realizing that 'A' wouldn't be Alison, the girls began searching for clues. Their initial suspect was Toby Cavanaugh, who took the fall for an incident the girls refer to as 'The Jenna Thing'. After an attack from her boyfriend, Ben, Emily bonds with Toby. Emily begins to believe Toby may not be Alison's killer, later confessing to him that she is a lesbian. Emily then starts going out with Maya, later developing a relationship with her. Emily later confesses to her parents about Maya and her sexuality, leading to a conflict between her and her mother. Maya was later sent to juvenile detention following the discovery of marijuana in her bag by Emily's mother. Toby is arrested for Alison's murder, but claims that he met Alison the night she disappeared to thank her for what she did. It is revealed that Jenna, Toby's stepsister, forced him into a sexual relationship. Emily decides to hold a memorial for Alison; however, the memorial was later destroyed, and a picture of her at its remains made her a suspect. Emily subsequently reveals her feelings towards Alison, after Detective Wilden tries to pin Alison's murder on her.

Meanwhile, Aria attempts to tell the truth about her father to her mother, but 'A' tells her mother before she could. This led to her parents' separation and her brother, Mike's, change in behavior.

Meanwhile, Melissa breaks up the engagement with Wren after seeing him kissing Spencer, leading to a conflict between the two sisters.

Hanna attempts to make her boyfriend, Sean, forget the old her, but it backfires.

The girls' next suspect was Noel, after Hanna is hit by a car while spying outside Mona's birthday party. Hanna witnesses Noel writing a message at the back of a car, owned by Ezra. Noel blackmails Ezra about his relationship with Aria, but is later framed by 'A' for cheating on exams. Hanna and Sean later break up, after Hanna dances with Lucas at the dance-a-thon fundraiser (as 'A' demanded). Ian returns in town, later reconciling and eloping with Melissa, to the surprise of the girls. Hanna later enlists Caleb's help to work on Emily's phone in order to talk to Maya. She eventually sympathizes with him after discovering his poor home life and develops a relationship with him. However, she breaks it off after she discovered that he was working for Jenna. Emily comes across Paige, a teammate of hers who began making homophobic remarks to Emily, though she later reveals herself as a lesbian. She and Emily later began dating, although Paige wants to keep things a secret. She and Emily later break up, and Emily dates Samara.

The girls discover that Ian was the guy Alison was seeing the night she disappeared and suspect he was the one who killed her. After finding more clues, the girls, with Garett's help, set up a plan to blackmail Ian, but this backfires when Ian sends someone to meet them in his place. Spencer is confronted by Ian at the church. He corners her at the bell tower, attempting to kill Spencer. However, a mysterious figure pushes Ian off the tower, presumably killing him.

Main cast

 * Troian Bellisario as Spencer Hastings
 * Ashley Benson as Hanna Marin
 * Holly Marie Combs as Ella Montgomery
 * Lucy Hale as Aria Montgomery
 * Ian Harding as Ezra Fitz
 * Bianca Lawson as Maya St. Germain1
 * Laura Leighton as Ashley Marin
 * Chad Lowe as Byron Montgomery
 * Shay Mitchell as Emily Fields
 * Nia Peeples as Pam Fields2
 * Sasha Pieterse as Alison DiLaurentis3

Recurring cast

 * Keegan Allen as Toby Cavanaugh
 * Tammin Sursok as Jenna Marshall
 * Janel Parrish as Mona Vanderwaal
 * Torrey DeVitto as Melissa Hastings
 * Ryan Merriman as Ian Thomas
 * Chuck Hittinger as Sean Ackard
 * Tyler Blackburn as Caleb Rivers
 * Brendan Robinson as Lucas Gottesman
 * Brant Daugherty as Noel Kahn
 * Lesley Fera as Veronica Hastings
 * Cody Allen Christian as Mike Montgomery
 * Lindsey Shaw as Paige McCullers
 * Bryce Johnson as Darren Wilden
 * Diego Boneta as Alex Santiago

Guest cast

 * Julian Morris as Wren Kingston
 * Nolan North as Peter Hastings
 * Jim Titus as Officer Barry Maple
 * Yani Gellman as Garrett Reynolds
 * Eric Steinberg as Wayne Fields
 * Jill Holden as Mrs. Welch
 * Amanda Schull as Meredith Sorenson
 * Carlson Young as Amber Victorino
 * Parker Bagley as Jason DiLaurentis
 * Anne Marie DeLuise as Jessica DiLaurentis
 * Roark Critchlow as Tom Marin
 * Tilky Jones as Logan Reed
 * Patrick J. Adams as Hardy

Development and production
Originally developed as a television series by book packaging company Alloy Entertainment, the idea was described as "Desperate Housewives for teens." Alloy met with author Shepard, and gave her the property to develop into a book series. With Alloy and Warner Horizon interested in producing a Pretty Little Liars television series for years, it was first planned for The WB in 2005 with a different writer. The first novel was published by HarperTeen in October 2006. In June 2008, Alloy noted that it was developing a Pretty Little Liars television pilot for ABC Family. The novels are being adapted for television by I. Marlene King.

Casting
ABC Family began casting for a Pretty Little Liars television pilot in October 2009. Lucy Hale was cast as Aria Montgomery in the project, followed by Troian Bellisario and Ian Harding (as Spencer Hastings and Ezra Fitz, respectively) in November 2009. In December 2009 The Futon Critic confirmed the casting of Ashley Benson as Hanna Marin and Shay Mitchell as Emily Fields, as well as the addition of Laura Leighton as Ashley Marin, Alexis Denisof as Byron Montgomery, Bianca Lawson as Maya, as well as Jean Louisa Kelly and Nia Peeples. The Hollywood Reporter also noted that Torrey DeVitto and Sasha Pieterse landed recurring roles in the pilot.

The Alloy website later confirmed that Pieterse would be playing Alison DiLaurentis and DeVitto would be Melissa Hastings, also noting Janel Parrish as Mona Vanderwaal and Cody Allen Christian, as Mike Montgomery. In April 2010, Chad Lowe replaced Alexis Denisof as Aria's father, Byron Montgomery. Also in April, Holly Marie Combs was cast as Ella Montgomery.