When one of their tightly-knit group mysteriously disappears, four high school girls find their friendship difficult to maintain when they begin receiving taunting messages from someone who seems to know everything about their past and present secrets.

Best friends Spencer, Aria, Emily, and Hanna find themselves under suspicion when the mysterious stranger named A tries to blame one of the girls for the death of their friend Alison and threatens to reveal the girls' darkest secrets.

Aria, Emily, Hanna, and Spencer find their lives unraveling when A's plans change and the girls are taken to the police for questioning.

Struggling to return to normalcy after surviving Alison's attempt to kill them, Spencer, Aria, Emily and Hanna endure a series of disasters before realizing that they are being stalked by a new "A" who knows all of their secrets.

In the weeks leading up to Ali's murder, Ali reveals her plots against Emily, Hanna, Aria, and Spencer, as well as a dark secret that has the potential to destroy everything.

After surviving their latest encounter with A, high school seniors Aria, Emily, Spencer, and Hanna must try to convince the police that the real A is still on the loose, all while trying to stay alive.

Hanna, Spencer, Emily and Aria are trying to move on and forget about their old friend Alison DiLaurentis and all the torture she put them through, but someone is trying to keep her spirit alive.

After high school juniors Spencer, Emily, Hanna, and Aria think they have seen Ali, their missing and presumed dead friend, they pursue clues from a mysterious stalker, trying to find out if she is still alive.

After seeing a girl who looks just like herself in a violent video, Emma, who lives with a foster family, begins a search to find out what happened to the girl.

Poppy, Aster, Corrine, Natasha, and Rowan are the heiresses of the Saybrook's jewellery empire, a family business that is known for both its wealth, and a very old curse that leads to family members dying suddenly. When one of the 5 heiresses is killed, and an online gossip site publishes a statement "One Heiress Down, 4 more to go", an investigation is opened.