Last summer while Spencer was taking AP courses at Penn, she began taking speed pills as a way to help with studying. After being arrested by the police for possession, she arranges for Hanna to help her frame her roommate, Kelsey, as a dealer, in order for Spencer to not face charges. After landing the role of Lady Macbeth in the school play, the stress and guilt begin to take their toll on Spencer, causing her to have frequent hallucinations in which she is haunted by Kelsey and Tabitha. She becomes paranoid and begins to believe Kelsey is "A" and is taking revenge on her for being framed. Emily accidentally meets Kelsey at a party and is instantly smitten with her. She and Kelsey grow close, much to Spencer's disapproval. After Emily is hurt by Spencer's remarks about her love for Alison, she angrily tells Kelsey that Spencer framed her for the drug possession. Depressed, Kelsey overdoses and attempts to throw herself into the quarry where Mona died, but Emily saves her and Kelsey is sent to the Preserve for treatment. While visiting Kelsey, the girls realize that Tabitha was also a patient at the Preserve and was the same age as Alison and Courtney.Hanna's father her on to help with the social media aspect of his campaigning. She meets a boy named Liam, who she falls for, despite knowing he is the son of her father's political opponent. They break up when she learns he has been seeing multiple other girls while dating her, and reconciles with Mike. And after Aria is dumped by Noel, she seeks out comfort in Ezra, in hopes of rekindling their romance. However, things are strained between them, and Aria eventually enters back into a relationship with Noel, after discovering Ezra and Klaudia being intimate.The Liars attempt to circumvent "A's" threats by coming clean about their secrets, with varied success. Meanwhile, "A" becomes more violent, attempting to kill Emily by pushing her off a small cliff earlier in the book, and swears she saw a blonde when this whole ordeal happened. A later sends Spencer an email of Tabitha on the beach with a head injury, indicating that "A" was the one who disposed of Tabitha's body. "A "taunts the Liars, stating they will NEVER discover A's true identity.