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.

After their missing friend's body is found and another of their friends commits suicide, four former best friends live in fear of their secrets being exposed by someone who is stalking them via their cell phones.

The stalker's identity has finally been revealed, but Spencer, Emily, Hanna and Aria are bound to repeat the past, and continue to be bad.

As the third season begins, a summer has passed since Aria, Emily, Hanna and Spencer found out about Mona being ''A'' and the death of Maya. With the terror seemingly over and an alleged murderer now behind bars, the town of Rosewood is slowly healing from old and new wounds. Now back together and coming upon the second anniversary of Alison's disappearance, the girls find themselves back on the defensive when a shocking event rocks Rosewood.

Four friends band together against an anonymous foe who threatens to reveal their darkest secrets.

Four friends band together against an anonymous foe who threatens to reveal their darkest secrets.

A collection of four stories from Sara Shepard's Pretty Little Liars series, chronicling the adventures of Hanna, Emily, Spencer, and Aria during the winter break between "Unbelievable" and "Wicked."

The drama continues as season two begins moments after the explosive season one finale. The girls are the talk of the town -- and not in a good way. Whoever said that change is good has never visited Rosewood, PA ... or come across four pretty little liars.

Follows the lives of four teenage girls as their friendships and other relationships are strained by the appearance of a mysterious person threatening to tell their darkest secrets to the public.

Deciding to come clean about a terrible mistake they committed during spring break, high school seniors Aria, Emily, Hanna, and Spencer hope to end the blackmail of a ruthless stalker who retaliates by plotting a murderous revenge.