1x01 — Pilot

Friends Aria Montgomery, Emily Fields, Hanna Marin, and Spencer Hastings grow apart when their clique leader Alison DiLaurentis goes missing. A year later they all begin receiving messages from the mysterious "A", who threatens to reveal their darkest secrets. They soon suspect that Alison is "A", until her body is finally found and the messages continue.

1x02 — The Jenna Thing

With Jenna's return to Rosewood, the girls are forced to face an unpleasant incident from their past that sealed their friendship forever, especially since "A" won't let them forget it. Meanwhile, questions about the night of Alison's disappearance begin to arise, as the events of that fateful night continue to haunt Aria, Spencer, Emily and Hanna.

1x03 — To Kill a Mocking Girl

The girls try to pay tribute to Alison's memory, but they are still faced with unresolved issues. Aria has an unpleasant encounter with her father's former mistress, and Spencer must face a vengeful Melissa. Hanna is trying desperately to get her boyfriend to forget the 'old Hanna'. But with "A" taunting them every step of the way, the girls will find that leaving the past behind is much harder than they first thought.

1x04 — Can You Hear Me Now?

The girls block e-mails and text messages from all unknown users in an attempt to stop "A," but their problems are far from over. One girl receives a surprise visit, while another receives a gift from a prospective paramour. And just when things couldn't get any more complicated, the girls find out that trying to keep "A" away comes with a price.

1x05 — Reality Bites Me

Aria forgets her cellphone in Mr. Fitz's apartment, and after he reads a message from A, he decides to break up with her rather than risk being fired. Hanna has to work in a dentist office to pay for the damage she did to Sean's car and gets some damaging information from A about one of her friends. Emily hides her budding friendship with Toby due to the girls' suspicion about him, hurting his feelings. Spencer's father tells her to throw a tennis match against a possible client and his daughter, and Ella deals with her husband's cheating.

1x06 — There's No Place Like Homecoming

When Emily decides to bring Toby as her homecoming date she soons finds herself in a possibly sticky situation with Toby and Maya, and at the same time, Aria is broken over her hidden-relationship with Ezra. Meanwhile, the girls must face a heartbreak, a boyfriend's virginity and some disturbing information that involves Toby and Jenna's relationship.

1x07 — The Homecoming Hangover

Aria's brother, Mike, doesn't take it very well that his parents are separating, which makes him fight in school after his mother decides to not watch his game. Emily decides to give a shot on dating Maya. Hanna and Sean make-up, but she's more interested in Lucas. Spencer and Alex have some fun in the country's club kitchen. At last, A has still one more creepy message to deliver to the girls, which makes them assume that Toby might be dead. Sara Shepard, writer of the Pretty Little Liars book series, makes a special appearance in the episode as a substitute teacher at Rosewood High School.

1x08 — Please, Do Talk About Me When I'm Gone

As new evidences about the day that Alison died comes to the surface, Spencer gets some damaging information from Alison's brother, Jason. Aria agrees to go out on a double date with Hanna and Sean's friend Noel, and the evening takes an interesting road once Aria realizes that Noel is way more than just a pretty face. Emily and Maya’s relationship blossoms when Emily asks Maya on a date. Due to the Marins' financial problems, Hanna's credit card gets declined, so she decides to put up a lot of her old clothes and handbags up for auction online with the help of new ally Lucas. Meanwhile, the girls begin to prepare themselves for Alison's memorial day, but once they find out that Jenna will be the one to deliver a speech about Alison, they all get scared. Later that night, a mystery person comes out and destroys Alison's memorial.

1x09 — The Perfect Storm

A terrible storm comes to Rosewood, and all of the students are trapped in school. Emily reveals a secret after she's accused of killing Alison. When Aria is about to give Noel a chance on dating her, Ezra returns. Byron leans on Ashley for advice as his relationship with Ella only gets worse. Meanwhile, Spencer discovers something that her mother has been keeping from her. And at the end of the episode, Lucas tries to tell something to Hanna, and his shoes are dirty, suggesting that he was at Alison's memorial.

1x10 — Keep Your Friends Close

When new evidence leads the FBI to believe that Toby killed Alison, he tries to tell Emily his side of the story. Spencer tries to mend fences with sister Melissa, just as her ex-boyfriend Ian returns. Aria begins to develop feelings for Noel, which complicates her relationship with Ezra even more, until he admits his feelings for her. Ashley's financial problems are bringing her to the brink. Meanwhile, the girls go "glamping" for Mona's birthday in hopes of closing in on "A", but when "A"'s identity is revealed to Hanna, she is hit by a car before she can tell the others.

1x11 — Moments Later

Moments after Hanna is hit by a car, the girls’ world is turned upside down. “A” is no longer content to playing a game of cat and mouse – it has taken a far more precarious turn and now more than ever the four Pretty Little Liars have to turn to each other for support. With Hanna in the hospital and armed with the information of who “A” is, the girls are backtracking to figure out how they got to this point. How could this person know everything and want to use it against them? Meanwhile, each girl has to also deal with a secret that is either found out, confessed or confronted – proving that secrets are still abound in Rosewood, PA.

1x12 — Salt Meets wound

Hanna's return home from the hospital should be a joyous event, but being stuck in a wheelchair and feeling haunted by "A" makes her return feel more like a Hitchcock nightmare than a proper homecoming. Even though the girls try to put on their best effort to support Hanna, they all have troubles they have to face as well: Spencer is still reeling from Melissa's surprise, when an unexpected roadblock is thrown up in her relationship with Alex; Emily, on the other hand, is hoping that an introduction to Maya during a tense family meal will smooth all apprehensions her parents may have. Meanwhile, blackmail is in the air when Aria and Fitz suspect a student is on to them.

1x13 — Know your frenemies

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. And Spencer must now handle the return of happy newlyweds Melissa and Ian, even though her suspicions of Ian's ties to Alison grow. But with the other girls' support and unexpected help form an unlikely source, the future for the Liars doesn't look so hopeless. Meanwhile, "A" has Hanna jumping through old habit hoops with regard to the stolen money. Will Hanna fall back into her old ways, or does she have the will power to stand up to "A" and her games?

1x14 — Careful What U Wish 4

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? Emily can only think of Maya and is desperate to speak to her -- so much so that she enlists the help of Caleb, the new bad boy in the school. And as an important piece of property goes missing, Spencer finds being in close quarters with her new brother-in-law, Ian, more difficult than ever. Meanwhile, Aria's former babysitter, Simone, comes back to town for a surprise visit. But what should be a happy reunion quickly becomes a nightmare for Aria when Simone sets her sights on Ezra.

1x15 — If At First You Don’t Succeed, Lie, Lie Again

The girls try to resume a sense of normalcy in their lives, but even the simple tasks of dating and extra-circular activities meet with strife. Emily must deal with a jealous teammate who is threatened by Emily's return to the pool, as Aria and Ezra plan their first date out in the open. And Hanna is still stuck playing "A's" game, but the next hurdle might just have complications for another Liar. With "A" pulling the strings and making matters worse, will the girls be able to weather the storm and lie their way out of it, or will they have to face the ugly truths? Meanwhile, Spencer turns to Ali's brother, Jason, for information about the night they believe Alison died, only to have to face part of her unpleasant past with Ali.

1x16 — Je Suis une Amie

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 (Lindsey Shaw) go for round two, as they are pitted against each other to compete for the anchor leg of the big race. And Caleb calls in his favor with a guilty Hanna as she tries to deter Aria from asking too many questions about Ella’s ticket to the museum opening. As secrets start to be revealed and antagonists become less threatening, will this become a game changer for the girls? Meanwhile, Spencer takes on the task of tutoring a fellow student to try and get some answers.

1x17 — The New Normal

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? And don't forget about the last liar who is getting way too comfortable with someone she might not want to trust. Whatever it is, "A" is sure to have something to say about it. It's now just another normal day in Rosewood, PA for Aria, Emily, Hanna and Spencer.

1x18 — The Badass Seed

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? Or is it an unknown stranger who is playing puppet master with four girls' lives? Only time will tell who the Bad Seed is. Meanwhile, Aria sees the school play as an opportunity to get closer to Ezra. But will her plan backfire and put her relationship in jeopardy?

1x19 — A Person of Interest

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? With the cops now demanding answers from Aria, Emily, Hanna and Spencer, will the girls come clean about "A," or are some secrets better left unspoken? Meanwhile, secret relationships take a toll on some of the Liars while others blossom. Love is not for the faint of heart.

1x20 — Someone to Watch Over Me

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.

1x21 — Monsters in the End

Everyone has something to hide – whether it be a secret romance, who they really are and what their true intentions are. For Aria, Emily, Hanna and Spencer, keeping things hidden is second nature, but having to live with those secrets can become a big burden. How long can Aria be with someone when they can't go out in public? Is it a true friendship when Spencer and Toby aren't able to be seen together? How truthful can Emily be when she can't be honest about whom she wants to be with? And how can Hanna move on when she secretly still wants to be with the one who broke her heart? With someone like "A" out there to watch their every move, four Liars may not have to worry about keeping things hidden for too much longer. Meanwhile, Rosewood police officer Garrett Reynolds is keeping his promise to keep a close eye on the girls – much closer than they realize.

1x22 — For Whom the Bell Tolls

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? And with little more than a video and hazy memories of the night that Alison disappeared, the Liars may have to turn to an unlikely source of information to help them put a stop to "A" once and for all – or so they think.