Four girls whose clique falls apart after the disappearance of their queen bee, Alison DiLaurentis. One year later, they begin receiving messages from a mysterious figure using the name "A" who threatens to expose their secrets. At first they think it's Alison herself, but after she is found dead, the girls realize that someone else knows their secrets, â€" including long-hidden ones they thought only Alison knew.

This 'Book' Is For All The Pretty Little Liars Lovers Out There. Do not read if you haven't seen the series yet because there are spoilers :)