While new discoveries are made in the investigation of Charlotte's murder, the truth begins to emerge about the Liars' personal lives. Spencer is concerned to learn her mother is keeping a secret of her own. Aria confesses to Liam how deeply she's involved with Ezra's book. Ali admits that she and Elliott are more than just friends. Mona reveals where her true allegiances lie. Caleb, Spencer and Hanna deal with the complications of new relationships. Meanwhile, Emily and Hanna each receive shocking threats that elevate the seriousness of the situation.