Meet the Pretty Little Liars. There's Aria Montgomery, Spencer, Hanna and Emily. When their best friend Alison goes missing they begin receiving text messages from an person known as 'A' who is planning to reveal all their secrets which only Alison knows. They quickly begin to suspect Alison is the one behind the text messages but they might have the wrong person. Other characters include Ella Montgomery, Byron Montgomery, Melissa and Pam Fields.
Aria Montgomery, Hanna Marin, Spencer Hastings and Emily Fields are receiving more text messages, e-mails and notes from A. The four of them start thinking up who A could be. The four girls start talking about The Jenna Thing and what they did to Jenna Cavanaugh who is blind. Aria is still having an affair with her teacher Ezra. Emily starts dating Maya.
The Pretty Little Liars keep receiving more text messages, e-mails and notes from the mysterius 'A'. The notes make them all think of who can be 'A' but they all come up with different suspects. Several residents of Rosewood look guilty but are they 'A' who is that just what 'A' wants them to think to throw them off track.
After receiving more and more messages, notes and emails from 'A', The Pretty Little Liars continue to do what the notes say. Hanna's father comes to Rosewood. Ella Montgomery is trying to reconnect with her daughter Aria after she found out her husband Byron was having an affair with Meredith and Aria knew all about it.
The Pretty Little Liars keep receiving more and more notes from the mysterious 'A'. The four girls keep seeing quick flashes of blond hair and keep hearing a girl giggle, which they think is Ali, but when they look again there is nothing and the voice is gone. They think they are all going crazy but they quickly realise that is what 'A' wants.
While the homecoming decorating committee is knee deep in balloons, the four friends from Rosewood are just trying to stay afloat. Dealing with heartbreak, a boyfriend's virginity pledge and a vengeful sister all takes a backseat when one girl makes a shocking homecoming date choice that puts her in a possibly sticky situation.
Spencer, Aria, Emily and Hanna must deal with the consequences of their disastrous homecoming dance. Family, friends and boyfriends are all in flux, and the girls need to act fast to prevent the situation from getting worse.
The girls are ready to say goodbye to Alison as her memorial service approaches. However, Alison's brother Jason shows up and the gang quickly finds out that saying goodbye is the last thing he wants to do. The clique wants to celebrate Alison's life in a peaceful and positive way, but with Detective Wilden back on the scene and Jason taking over the girls realize they may not have prepared for what is to come.
Rosewood gets a massive storm on the day the students are to take their SAT test, which causes the school to postpone the examinations. Trapped in the school during the storm, the girls' personal lives become stormy as well. Drama strikes each girl differently and manifests itself into different situations.
"A" targets the girls once again as they attend an upscale camping trip for one of their friend's birthday party and they fear that "A" may want to crash the fun. The FBI becomes involved in Alison's murder case because of new evidence that they have found. Also, Ashley faces difficulties because of her financial situation.
Aria, Emily, Hanna and Spencer and those around them, must deal with the aftermath of what happened in Rosewood, PA one mysterious night.
Hanna is released from the hospital, but confined to a wheelchair. Meanwhile, Aria struggles with the fact that Noel knows about her affair with Ezra, Spencer's relationship with Alex hits a road bump, and Emily invites Maya to meet her family.
Relationships are in flux in Rosewood, PA as the Liars face many obstacles. As Noel steps up his pursuit of Ezra and what he can gain from his knowledge, Aria and Ezra start to feel like there may be no way out. Emily must also deal with opposition to her love life, as her mother Pam's perceived tolerance of Maya comes to a screeching halt.
As the school gets ready for the dance-a-thon, Aria, Emily, Hanna and Spencer have more on their minds than raising money for the school trip to Washington, DC. Hanna is having a hard time finding a job to help her family's financial situation, but when "A" has a job for her, will Hanna be able to refuse?
The Liars try to retain some normalcy in their lives, but even everyday activities are filled with drama. Emily is forced to deal with a teammate who is threatened by her return to swimming, while Aria and Ezra make plans for their first date in public.
A crucial swim meet for the Rosewood Sharks is the setting for Aria, Emily, Hanna and Spencer to experience a lot of turmoil. Emily and Paige go for round two, as they are pitted against each other to compete for the anchor leg of the big race.
What happens to one liar when parent-teacher conferences come around and her father sits face to face with the love of her life? What about when another one reaches out to a tarnished innocent, when no one else will? And what about the liar who is taken by surprise by an unpleasant person?
As their doubts, fears and suspicions grow, Aria, Emily, Hanna and Spencer start to wonder what the true face of evil looks like. Is it the girl who holds a grudge and will do anything to keep her loved ones near? Is it the new brother-in-law who might have a darker side beneath the surface?
After a shocking revelation from the police, the spotlight is turned on four little liars who look to be crying wolf. But with everything pointing to Ian, how could the girls be wrong? Or could this be just another game "A" is playing with them?
As the heat is turned up on the suspicions surrounding Spencer, the girls must come to the reality that they aren't the only ones hiding secrets in Rosewood.
Rosewood police officer Garrett Reynolds is keeping his promise to keep a close eye on the girls – much closer than they realize.
Now that Aria, Emily, Hanna and Spencer are in possession of the information that Alison left them, the girls decide that it's time to finally put an end to "A" and the mystery surrounding their friend. But without certain proof that their hunch is right, how can the girls catch "A" in his/her own game?