Spencer has some exciting news to share with her friends on the night before their graduation from seventh grade. Her parents have given her permission to use her sister's bedroom, a converted barn separate from their house, for a sleepover. After she tells Aria, Hanna and Emily, they all troop over to their ringleader Alison's house.
Alison, or Ali as her friends call her, is up in her bedroom reading a notebook. She won't share what's in it. Before Spencer can tell her the plan, Ali's mother interrupts them. She wants to talk to her daughter in private. The girls sense that Ali is in trouble as they gather on her patio to wait. When she reappears, Ali seems disorientated. She's also changed clothes. Ali tells the girls not to be concerned. Her mom was angry because she made a mistake with the laundry, but their sleepover can go on as planned.
Ali's excited to learn they'll get to use the barn for their party. The girls spy Melissa, Spencer's sister, cutting through the back yard. Ali asks her if she's excited about her upcoming trip to Prague and if she's taking her boyfriend, Ian, with her. Spencer gets angry because she thinks Ali is purposely trying to get her in trouble with her sister, as Spencer recently kissed Ian; a secret no one knows but Ali. Ali continues to bait Melissa, asking her if she thinks it's a good idea to leave Ian behind as he might get another girlfriend. Melissa doesn't answer Ali, but makes a point to look at the giant excavation hole in Ali's back yard before heading to her own home. Ali crows that this will be the best summer ever. For all of them.
The friends think they might make their friendship even stronger now that their fears from last year — that someone would discover they were involved in a bottle rocket accident that blinded their neighbor, Jenna — seem to be unfounded.
Three years later, Aria wakes up in a hospital waiting room. She's waiting for news about her friend Hanna, who was hit by a car the previous night. Aria knows that it was the mysterious "A" who tried to kill Hanna. A has been sending threatening texts to Aria and her friends for several weeks, and Hanna was meeting Aria, Spencer and Emily to tell them who she believed A was.
After Hanna was hit, Aria and Emily received a message saying that she knew too much. A doctor finally comes out to explain to Hanna's parents about her prognosis. Hanna has a broken arm, some internal injuries and is in a coma. The doctor is unsure about the extent of her brain injuries.
Aria believes she knows who may have killed her friend Ali. She asks Officer Wilden if she can talk to him, away from the others. Officer Wilden is not only dating Hanna's mother, but he is also investigating Ali's murder. Before Aria can voice her suspicions, Wilden tells her that the police aren't going to press charges against her teacher/lover, Ezra. Aria's ex-boyfriend Sean told the police that a high school teacher was having an affair with a student after he received pictures of Aria and Ezra kissing. Officer Wilden warns her that he probably should tell her parents what happened, but Aria begs him not to. After all, she doesn't want to press charges.
She then tells Officer Wilden her suspicions that Spencer killed Ali. Aria figured out that Ali had been secretly dating Ian, the boy Spencer had a crush on. Aria admits Spencer and Ali got into a big fight the night of the sleepover. They left the barn, and Spencer didn't come back for more than 10 minutes. Ali disappeared that night. Officer Wilden convinces Aria that Spencer couldn't have done the murder because she would have had to drag Ali's body across the lawn to the hole in Ali's yard. A young girl in seventh grade wouldn't have had the strength to do that, and then return to her other friends without appearing tired or upset. Officer Wilden is interested to discover that Ali was dating Ian, however, as that would give him or Spencer's sister, Melissa, a motive for the murder.
As Aria contemplates how A's past texts led her to believe Spencer was the murderer, she feels a hand on her shoulder. It's her estranged father, Byron. When he saw the news report, he tried calling for Aria at her mother's house, but her mother threw her out the previous week. Byron offers to let her live with him and his girlfriend, Meredith.
Spencer has a troubled night full of dreams about her argument with Ali and about Hanna's accident. Spencer had hoped someone would call her with news about Hanna's condition, but no one had so far. Between her recent ability to remember the argument, A's texts hinting that Spencer killed Ali, and then the argument the night before in which Spencer pushed her sister down the stairs, Spencer is emotionally unstable. Her mother calls her into the kitchen where Spencer is surprised to see Melissa, home from the hospital. Spencer's mom tells the girls that they won't be seeing their therapist anymore. Also, although Spencer plagiarized Melissa's paper for a class and is now up for a major award, the whole family will keep the matter quiet. Not only will Spencer not admit her crime, but her parents also expect her to win the award. Finally, their parents are taking the girls to their grandmother's house on the beach. They hope the weekend away will help the girls get along.
Emily's parents have sent her to live with her ultraconservative aunt and uncle in Iowa, because she continued to see Maya, the girl she loves. Emily tries to make conversation on the long ride to their house from the airport, but her aunt and uncle don't speak to her. They live on a solitary farm, and their six children are home-schooled. Her aunt takes away Emily's cellphone so she has no way to contact Maya or find out how Hanna is doing. She will be sharing a room with her cousin Abby.
Although Abby pretends to be a willing follower of her parents' beliefs, she surprises Emily by asking if she wants to sneak out with her two older brothers after their parents go to sleep. They take her to a party at an abandoned silo. All the kids drink and dance. Emily meets Trista, a beautiful blond girl who flirts with her. Emily finds herself very attracted to Trista but wonders how she could so easily forget about Maya. For the first time since she arrived, she's glad to be in Iowa, as there's no hope that A will be able to spy on her here and send her texts.
Aria stops by Ezra's house so she can leave him a note to tell him where she'll be living. She's surprised to find him at home. She's devastated to learn that he's been fired and will be moving to Rhode Island. The two kiss passionately. Aria wants to move with him, but he tells her that she should look him up in a few more years. He gives her his Shakespeare bobblehead as a keepsake; it's one of his favorite possessions. Later that day, Aria moves into her father and Meredith's apartment. It's an eclectic mix of Meredith's artwork and secondhand furniture. Aria has to sleep in Meredith's studio, as there's no extra bedroom. Aria is uncomfortable with how different her father is with Meredith. He dresses better, eats better and takes vitamins. He tells Aria that Meredith wants her to take a class at the college where he teaches. Meredith gets a class free each semester, and she's giving it to Aria. When her father leaves the table, Meredith makes it clear that no matter how much Aria doesn't like the situation, he and Meredith are staying together.
Spencer and her family head to the shore, but neither Spencer nor her sister want to spend time together. Their parents leave them alone, but Melissa talks on her cellphone while Spencer hides in her room. Mona calls to tell Spencer that Hanna is in a coma. Mona asks if Spencer will help organize a candlelight vigil, and Spencer agrees to do whatever she can as soon as she gets back home. After she hangs up, Spencer hears a strange tapping that sounds like someone is outside and trying to get in. Scared, she finds Melissa, and the two go up to their old playroom so they can have a better view of the yard. They're just in time to see a seagull run out of a drainpipe.
The two reminisce about the games they used to play in the room. Spencer apologizes for using Melissa's paper for her assignment. Melissa says their parents will probably buy Spencer a great gift if the essay wins the Golden Orchid. Spencer is surprised when Melissa says she's not angry anymore. Melissa finds an old bottle of vodka that she and Ian hid in a cabinet years ago. She and Spencer both have a drink.
Spencer tells Melissa about the time she kissed Ian in their driveway. She promises it only happened once. Melissa claims she knew that Ian had kissed her. She also knew about Ali and Ian's affair. Spencer then tells Melissa about the argument she and Ali had and how she is afraid that she'd killed Ali. Melissa tells her not to worry: It takes a unique person to kill, and Spencer's not unique. As she says this, Melissa rips the head off a doll that looks exactly like Ali.
Aria arrives at Hanna's hospital room the following Monday to find Lucas already there, reading a magazine aloud to Hanna. Unbeknownst to Aria, Lucas and Hanna had shared several intimate moments in the days before Hanna's accident. Lucas tells Aria that although there's been no official change, some of the readouts showed Hanna may have woken up in the night. He leaves the room to get something to drink. Spencer arrives, and Aria grills her about where she's been since Saturday. At first, Aria still suspects Spencer may be A, but the more they talk, the more she agrees with Officer Wilden. Aria is shocked to learn that Spencer and Melissa both knew that Ali was dating Ian. Aria realizes that Melissa also fits the clues A had sent her previously, but she doesn't say anything to Spencer. As she stands by Hanna's bed, Aria thinks she sees someone spying on them, but can't prove anything when she looks closer.
Emily's aunt and uncle found out about the teens' party. When they question their children, Emily's cousins tell their parents it was Emily's fault. She'd heard about the party with the public school kids and insisted Abby take her to it. The older boys went with them to make sure they were safe. Emily's aunt and uncle call her parents to tell them they're sending Emily back to Pennsylvania. Emily is so angry she packs her things and leaves before they can take her to the airport. She's afraid if she goes home, her parents will send her to a convent or military school.
Aria has decided to take an abstract art class in which students will be learning to free their minds from visual cues for creating and instead use their other senses. In the first lesson, the teacher turns out the lights and has the students locate the person nearest to them. They are instructed to hold hands for a few minutes to try and picture what the person's face looks like from how their hands feel. Then, the teacher turns on the lights and has them draw the face they've seen in their heads. When they are finally allowed to look at their partners, Aria is horrified to see Jenna Cavanaugh, the girl Ali blinded with a bottle rocket.
Hanna has been having vivid dreams about the night before Ali disappeared. She keeps trying to warn Ali not to go to the sleepover because she's going to be killed, but Ali only laughs and tells Hanna that she's not dead. The dreams are so real, Hanna can feel Ali's hand in hers and her breath on her cheek. As she tries to warn Ali again, her friend assures her that things aren't always what they seem. Hanna opens her eyes and is confused by the pain she's in and the presence of her family and friends. She doesn't remember the hit-and-run. The last thing she remembers is getting the dress at the mall for Mona's party.
Emily hitches a ride to the bus station and buys the first ticket out of Iowa. Unfortunately, it's to Akron, Ohio. She doesn't know anyone in Ohio, so she finds herself sitting in a diner across from the terminal, trying to decide what to do next. A news story on the television explains that Hanna has woken up from her coma. It goes on to flash a picture of Emily. The reporter explains that another friend of murder victim, Alison DeLaurentis, was discovered missing from her relative's home this morning. Emily's parents then appear. They tell the cameras that they love Emily and plead with her to come back. Emily hurries to the bus station to buy a ticket home.
Hanna is being thoroughly obnoxious to her doctor and the staff at the hospital. She hates that her face has been cut and worries that the intravenous fluid they're giving her will make her fat. Aria and Spencer arrive, hoping that Hanna can tell them who A is, but Hanna can't remember anything. Mona arrives, and the conversation quickly turns to the vigil she had planned. Hanna suggests they turn it to a welcome-back party instead. She's still upset that she can't remember Mona's birthday party, but Mona is reluctant to share details about what happened that night.
Spencer's stolen essay has made the finals of the Golden Orchid competition. Her parents have already made arrangements to travel with her to New York City for the final interview at the end of the week. Officer Wilden questions Melissa and Ian about the night Ali disappeared. Spencer eavesdrops. She can't believe Melissa doesn't tell Officer Wilden about Ali and Spencer's argument. Ian admits he had flirted with Ali, but denies that they were in a relationship. Spencer begins to wonder whether Melissa killed Ali.
Emily's mother picks her up from the bus station. Although she doesn't agree with Emily's choice of a homosexual lifestyle, she's decided to try and live with it. That's the advice Emily's mother got from reading a book by Dr. Phil. She also gives Emily a copy of Finding Nemo because one of the characters is voiced by a lesbian actress. Emily's mother drops her off at the hospital so she can visit Hanna. Aria and Spencer are already there, trying to help Hanna remember what she'd discovered about A, but Hanna just becomes more frustrated. Emily notices Hanna's cast is signed by just about everyone from their school. She leaves the hospital with Aria and Spencer. All the girls receive a text message from A telling them to stop searching for answers, or they'll have their memories erased, too. Emily notices the subject line is "kisses!" just like one of the signatures on Hanna's cast.
Spencer and Mona meet at the country club to discuss final plans for Hanna's party. Spencer is amazed at Mona's transformation. Ali had picked on her in middle school for being a dork, but Mona is now one of the most popular trendsetters at school. Before Spencer leaves, Mona confides she's been getting awful text messages from someone named A.
Mona stops by the hospital with a bunch of rowdy boys to cheer up Hanna. Lucas arrives with a bouquet of flowers, but everyone ignores him. One of the boys asks Hanna about the big fight she had with Mona. Mona tries to distract Hanna but then admits that they'd fought at her party. Mona finalizes plans for Hanna's party and gives Hanna a one-of-a-kind mask used in a runway show in New York City. Mona and the boys exit, leaving Lucas behind. He tells Hanna that Officer Wilden asked him questions about the night of Hanna's accident. He assures her he didn't tell Wilden about the texts she's been receiving. He also warns her not to trust Mona. Before he leaves, he kisses Hanna and asks if she remembers, but she has no clue what he's talking about. Lucas leaves without explaining.
Aria finds herself paired with Jenna, again, in their art class. Not wanting to admit they know each other, Aria gives a fake name. They have to make masks of each other's faces. Aria is surprised to learn that Jenna has a voice-activated cellphone that allows her to text people. The two girls talk during the class, with Aria opening up about her family problems. The discussion soon makes her uncomfortable so she flees the room. She gets a text from A warning her again not to tell what A did, or she'd be in the dark like Jenna. The text also says she should check out Hooters because Meredith works there.
Maya questions Emily about her time in Iowa, but Emily doesn't want to talk about it, afraid she might reveal something about Trista. Maya then gushes that she and Emily have been named the school's "best couple" for the yearbook. They'll pose for pictures the following day. Emily receives a text; it's not from A but Trista. Emily hides the text from Maya.
Mona and Hanna's old friends meet at Hanna's house, now that she's been released from the hospital. Spencer tells them that Mona's been receiving messages from A as well. As if to prove a point, Mona gets a text from A. It warns her to wait until she gets a belated birthday gift from Hanna before telling her what the fight was about at Mona's birthday party. When Hanna questions her, Mona admits they had a big fight, but it doesn't matter now. Spencer tells the girls that A is just trying to break them apart and that they shouldn't let this stranger do that to their friendship. The male models that Mona has asked to audition for "slaves" for Hanna's party interrupt their conversation. They'll carry Hanna in on their shoulders.
Emily is shocked when her parents invite Maya to come out with them for a "welcome home" dinner. Maya's natural charm soon relaxes everyone in the family but Emily, who has just received another flirtatious text from Trista. Maya follows Emily to the bathroom. Emily's nerves become even more frazzled when Maya suggests maybe Hanna's accident has upset her. Emily insists she's fine, but after Maya leaves Emily finds a note in her purse from A warning her to keep quiet. When Emily sniffs the note, she realizes it smells just like the gum Maya always chews.
Spencer and her parents, along with Melissa and Ian, spend the night in New York City before her interview with the Golden Orchid committee the following morning. Spencer can't get the image of Melissa ripping the head off the Barbie doll out of her head. She's also very nervous about the interview. She retires to the suite her parents have for her. She tries to relax, but finds it difficult. About an hour later, she hears a knock on the door to the adjoining suite. It turns out to be Ian. Melissa has passed out after drinking, and Ian wants to know if Spencer wants to go for a walk.
Instead, they sit on her bed and talk. Spencer asks him about Ali, but Ian insists they weren't dating — that they'd only hooked up a couple of times. He claims he preferred kissing Spencer. He wonders why she and Melissa are obsessed with the night Ali disappeared. Spencer wonders why Melissa is so concerned about it. Ian leans in seductively and tells Spencer they should stop talking about the past and make out instead. Spencer tries to talk him out of it, even though she enjoys his attention. Melissa knocks on the adjoining door. Ian makes a quick getaway to the main hallway, as Melissa comes in from her suite.
The following morning, Spencer must face the interview committee. At first things go well as she talks about her school accomplishments and various activities, but then her cellphone beeps. She was supposed to turn it off before the interview. As she reaches for it, she sees a message from A claiming that the judges can see she's a fake. It also suggests that Melissa killed Ali and wouldn't think twice about killing her. Spencer's momentum is thrown, and for several minutes, she stumbles through the next couple of questions. When asked what event has influenced her high school career the most, Spencer admits it was her friend Ali's disappearance and the recent discovery of her body. The interviewers seem stunned, but one approaches her later to tell her that he appreciated her honesty.
Emily and Maya participate in the photo shoot for the yearbook, but Emily is not into it. She still suspects Maya might have something to do with A's death. They stop to look at the photo spread that the yearbook staff wants to put together in memory of Ali. Emily is overwhelmed with emotion as she sees pictures of her best friend and first crush looking so happy and alive. Another photo spread is of the contents of students' backpacks and purses. One of them is of Mona's purse, and Emily notices a picture but can't make out whom it is because it's covered by other items. Emily gets a text from A threatening to tell Maya about Emily's crush on Trista if she says anything to anyone about A. Emily notices that Maya isn't in the room anymore and wonders again if Maya is actually A. Just then, Trista arrives. She hopped a plane with her father's frequent flier miles and wanted to surprise Emily. She hopes to attend the masquerade party that Emily had told her about.
Aria takes her younger brother to Hooters after school. When he discovers that she hopes they can confront Meredith together, he becomes furious. He blames Aria for their parents' breakup because she kept their father's affair a secret for so long. When he threatens to leave, Aria breaks down and tells him about A and all the threatening messages she's received. After a moment, he comes to Aria's defense and insists that she tell the police. Since Hooters is located next to the police station, there are several cops sitting in a booth nearby. He promises to keep her safe if A tries to do anything in retaliation.
Hanna is carried into the party on a pillowed platform supported by four man-slaves. Mona and Spencer welcome her to the festivities — a masquerade dance with a Monte Carlo gambling theme, complete with roulette wheels and card tables. Lucas arrives and sneaks Hanna away so they can spend time kissing in an alcove. When she hears Mona calling for her, Hanna insists she has to leave. Lucas tries to convince her that Mona is not a good friend, but Hanna doesn't want to listen. He tells her to make sure and find out exactly what Mona did to her at her birthday party.
When Hanna does ask Mona, Mona claims that it's the fact that she and Lucas dated for a summer between seventh and eighth. Mona says she never told Hanna because Lucas is a loser, and she didn't want Hanna to think she was a loser, too. Mona thinks he's trying to drive a wedge between them to get revenge. When Hanna confronts Lucas, he denies that he was ever serious about Mona. The three continue to fight when Hanna begins to remember the night of Mona's party. Although she realizes that Mona set out to humiliate her by having her wear a dress that was too tight and ripped; she also knows Mona has regretted her actions because she has done nothing but try and be Hanna's best friend. Hanna pretends to still have amnesia and sends Lucas away.
Emily and Trista arrive at Hanna's party. Emily told Maya that she and Trista were pen pals that happened to meet up again in Iowa. When Maya finds them at the party, she kisses Emily possessively in front of Trista. Trista acts like a kid at a candy store as she admires all the cute guys and all the girls' jewelry. Maya leaves for the bathroom. In her absence, Trista and Emily begin to kiss. Maya returns, upset at what she's seen. As Emily runs after her, she's approached by a police officer who tells her Aria has made a statement. He wonders if Emily has been receiving threatening text messages as well. Emily tells him she can't talk and races after Maya.
When she catches up to her, Emily asks Maya if she's been sending the texts. Maya claims to have no idea what she's talking about. She runs away again, and Emily receives another text telling her to check out the hot tub. A mermaid doll with X's on its eyes floats in it. A threatening message is scrawled across its head warning Emily to keep quiet or die. While Emily hides in the shadows, she sees Trista coming into the poolroom with a boy. The two make out on one of the chaise lounges.
Aria runs into the college art room to look for her cellphone. She's hoping to warn her friends that she's talked to the police. When Officer Wilden had asked her if there was anyone the girls may have hurt in the past that would want revenge, Aria thinks of Jenna. She keeps quiet about the incident, however. A thunderstorm rages outside as Aria searches the classroom. The masks the students have made have been put in their alcoves. Aria finds her cellphone in one as well. As lightening flashes, Aria sees one of the masks has been suspended from a tree branch, and it looks like a person. Its eyes have been crossed out and a sign tells her that since she told, Aria is next. With the next crack of thunder, the lights go out, and then the fire alarm in the building goes off. Aria tries to call the police, but drops her phone. Someone enters the classroom. Aria passes out when she discovers it's Jenna.
Spencer is having fun at Hanna's party until she thinks she hears Melissa's voice. Confused as to why her sister would come to a high school party, Spencer can't help but think again about A's clues that Melissa killed Ali. She tries to dismiss them, but between her angst and the glass of champagne she's had, Spencer decides she needs some fresh air to clear her thoughts. Melissa corners her in the bathroom and asks why Spencer lied to her again. Ian told her he was in Spencer's hotel room. Spencer swears that nothing happened between them. Melissa stomps away, and Mona comes out of another bathroom stall. She offers to wait for Spencer outside. As Spencer looks for an aspirin in her purse, she comes across an old picture of Ali and Ian standing next to each other with their arms entwined. A curse word and a threat on Ali's life are scrawled across Ali's face. The handwriting is Melissa's. Spencer gets a text from A telling her to be careful or she'll be dead, too.
Aria wakes up in the college classroom, panicking when she sees Jenna sitting next to her. Jenna calms her down and explains that Aria had a panic attack then fainted. Jenna tried to call for help but her cellphone wouldn't work in the storm, so she waited to make sure Aria would be all right. Aria admits her true identity, and Jenna explains that she already knew because she'd recognized Aria's voice. When Aria tries to confess about hiding Ali's secret, Jenna surprises her again. This time, Jenna tells how she and Ali had planned the prank with the firework as a way to get her stepbrother out of her life. Jenna was thankful to Ali for thinking fast that night and blackmailing Toby into taking the blame for the accident, even though the prank left Jenna blind.
Aria is sickened at the thought that Ali set up not only Toby, but also all of her friends. Jenna says that she and Ali weren't exactly friends, but that Ali understood Jenna's problems because she had sibling troubles, too. Jenna tells Aria that someone else saw the firework incident as well, but won't tell Aria who.
Emily, Mona, Spencer and Hanna find a secluded place to talk, and Spencer shows the girls the picture she found of Ali and Ian. Spencer decides she has to tell Officer Wilden about her sister's threats. The others warn her that it might be another of A's games and Melissa might not be guilty. Mona offers to drive Spencer to the police station since she doesn't have her car. The others want to go as well, but Mona convinces them to stay at the party because she's hired Justin Timberlake to sing.
Aria finds Emily and Hanna at the party. She tells them about her conversation with Jenna. As the girls process all that's happened, Hanna's faulty memory is triggered. Suddenly, the events preceding her accident flash through her mind, and Hanna remembers her final text from A, the one that came from a registered cellphone. The phone was Mona's. The girls re
alize they have to warn Spencer before Mona can harm her.
As Mona drives Spencer to the police station, she offers her a piece of banana-flavored gum. She admits that she got it from another student at school. Spencer begins to have second thoughts, but Mona convinces her to turn in Melissa for murder. Spencer receives a text from Emily warning her that Mona is A. Before Spencer can escape from the car, Mona realizes that Spencer knows her secret.
Hanna, Aria and Emily head to the police station to talk with Officer Wilden. As they are explaining the situation to him, he gets a call from Spencer. He picks up but doesn't talk. Instead, he puts the call on speakerphone so everyone can hear. Spencer has obviously dialed his number secretly and is using her conversation with Mona to give clues as to their location. After a shriek and the sound of tires squealing, the phone goes dead, but Spencer's given them an idea of where to start the search. The other girls insist on accompanying Officer Wilden.
Mona has thrown Spencer's phone out the window and changed directions in the car so that they now head for a different location. She takes Spencer to an abandoned quarry. There she explains how she and Jenna had been friends. Mona had seen everything the night of the bottle-rocket incident, even receiving burns on her stomach. Toby confessed to the crime so fast that no one, not even her parents, would believe Mona when she tried to tell them Ali did it. Even Jenna wouldn't admit that Ali was at fault. Mona and Jenna stopped being friends, and Mona became obsessed with getting revenge for her scars. She found her chance when she discovered Ali's diary among the stuff Maya's family was throwing out of the DeLaurentis' house. Ali had recorded all the girls' secrets. Mona can't explain how the cops never found Ali's diary and gloats over making Spencer and her friends squirm with her texts.
Mona tries to convince Spencer not to turn her in as A but to work with her instead. Mona has enjoyed becoming friends with Spencer. Together they can frame Melissa for Ali's murder. They could put Melissa in jail and then be A together, controlling all their friends. Mona then tells Spencer that the last thing Ali wrote in her diary was about a secret meeting she planned to have with Ian the night she disappeared. Ali threatened to tell everyone about their relationship if Ian didn't break up with Melissa. When Spencer refuses to become A, Mona attacks her. Spencer manages to flee from the car, but Mona tackles and then starts to strangle her. With the last of her strength, Spencer pushes her away, sending Mona hurtling over a cliff. Spencer falls to the ground, hits her head and is knocked out.
The police and other girls arrive to find Spencer nearly unconscious in front of Mona's car. Police dogs find Mona's body in the quarry below. Hanna discovers a plain cellphone and realizes it must be the one Mona used to send the messages from A. Hanna slips it into her purse. Meanwhile, Spencer refuses to go to the hospital. She gives her statement to Officer Wilden about Mona's confession and her belief that Ian killed Ali. She explains how Mona had Ali's diary that held all their secrets. The girls insist on accompanying Spencer home. After Officer Wilden drops them off at Spencer's house, she sees something in her backyard. The scene reminds her of the night Ali disappeared, and another memory comes to her mind. Ali got back up after Spencer had pushed her into the stone wall. Before they could argue again, Ali heard something and took off down a path. Spencer heard Ali giggle and saw two figures emerge from the trees. One was definitely Ali and the other was too big to be her sister, Melissa. Spencer could only assume it had been Ian. The girls gather in Spencer's backyard to see what's going on and overhear Ian and Melissa arguing. Hanna calls Officer Wilden to tell him where he can find Ian.
The following day, Aria watches the news with her father and Meredith. Meredith defends Aria's need to process everything that's happened, instead of discussing it with her father. Aria is grateful and thinks maybe Meredith isn't so bad after all. Aria's mother calls to apologize for her behavior and offers to let Aria come home. As Aria contemplates her next move, the scene of Ian on television in a courtroom distracts her. In the crowd, Aria is certain she sees Ali, only it's an older version of her friend. Aria convinces herself that she imagined the woman. As Meredith emerges from the bathroom, Aria's father asks if she's feeling ill. Meredith smiles and tells them it's OK because she's pregnant.
That evening, Officer Wilden comes to Spencer's house to question Melissa one last time. Melissa finally admits that she and Ian had been drinking the night Ali disappeared. Melissa had passed out. When she woke up, Ian wasn't there, but he was back in the morning. The next day, Melissa left for Prague. When she returned, she was too scared to admit the truth. Melissa breaks down sobbing, and Spencer realizes that both she and her sister share the same pressure to not disappoint their parents. Spencer comforts Melissa as their parents stand off to the side looking judgmental. When the call comes a few minutes later that Spencer has won the Golden Orchid, she knows what she must do. Although her mother still wants her to take credit for the essay, Spencer admits the truth.
A few days later, Hanna sits in her bedroom wishing she could call Mona and tell her she found the right foundation to cover up her stitches. She then recalls how Lucas had protected her the night of Mona's party and how they had kissed passionately in a school library. He hasn't called her after the events of the weekend, so Hanna figures he must still be angry with her. She calls him and leaves a message on his cell, asking if they can talk. Hanna's father comes to the house. He and Hanna's mother have some news. Her mother has been offered a job in Singapore. They give Hanna a couple options: She can stay at a boarding school in the area or move in with her father. He is willing to move to the house Hanna lives in now, but his fiancé and her daughter, Kate, would move in with them. Hanna says she'll think about the prospects. Officer Wilden arrives to take her to Ian's arraignment. Hanna gives him Mona's cellphone, but only after she's erased all of the messages to her.
The old friends meet up outside the courthouse for Ian's arraignment but first they dump all the "gifts" A had sent them into a garbage bag to give to Officer Wilden. The only thing Emily keeps back is the original love letter she'd sent to Ali. The girls then sit together in the courtroom and listen as Ian pleads not guilty to Ali's murder. As they hug one more time outside of the courthouse, Emily spies a chauffeured car with tinted windows parked nearby. One window is slightly rolled down, and Emily swears the eyes looking out at them are Ali's. Before the others can turn around to look, the car drives away.
An epilogue mentions that Emily found her true love in college, Spencer became a newspaper editor, Hanna married a billionaire, and Aria went off to live with Ezra in Europe. However, the girls still can't help but be bad, and a new A is ready to seek revenge.