Everyone knows Alison DiLaurentis, queen bee of Rosewood and famous "murder" victim. But what about Iris DiLaurentis, Ali's 15 year old sister? In the years Ali's been "missing", Iris was the only one she contacted. However, now that the liars know she's alive, Iris must try to convince Ali to come back and the liars to not fear -A. Because Iris knows everything. She's the missing link.

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.