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.

#1 New York Times bestselling series The second book in the #1 New York Times bestselling series that inspired the hit ABC Family TV show Pretty Little Liars. In ultra-exclusive Rosewood, Pennsylvania, four beautiful girls are hiding very ugly secrets. Spencer covets her sister's boyfriend. Aria is fantasizing about her gorgeous young English teacher. Emily is infatuated with the new girl at school. And Hanna is using some ugly tricks to stay amazingly...

#1 New York Times bestselling series The fourth book in the #1 New York Times bestselling series that inspired the hit ABC Family TV show Pretty Little Liars.Four pretty little liars' charmed lives have turned into living nightmares. Emily's been shipped off to Iowa to live with her überconservative cousins. Aria's boyfriend is behind bars-because of her. Spencer's afraid she was involved in Ali's murder. But Hanna's fate is far worse: She's clinging...

"Emily's been shipped off to Iowa to live with her überconservative cousins. Aria's boyfriend is behind bars--because of her. Spencer's afraid she was involved in Ali's murder. But Hanna's fate is far worse: she's clinging to life in the hospital because she knew too much. If these girls don't start listening to me, Hanna's going to look like the lucky one"--P. [4] of cover.

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.

Former best friends Hanna, Aria, Spencer, and Emily, who lost their best friend and leader, Alison, years ago when she disappeared, find themselves in grave danger when they pursue the truth about Alison.

#1 New York Times bestselling series The ninth book in the #1 New York Times bestselling series that inspired the hit ABC Family TV show Pretty Little Liars. It's been a year since the mystery of their former friend's disappearance was finally laid to rest, and Aria, Spencer, Hanna, and Emily have worked hard to put their lives back together. Now seniors in high school, the pretty little liars are older, but they're not any wiser. Last spring break...

Now seniors in high school, Spencer, Emily, Hanna, and Aria's friendship has been torn apart by new lies and stress, but they are drawn back together when anonymous messages threatening to reveal their secrets resume.

Rule number one of being an effective stalker: get to know your prey, the trouble they get into, the messes they make, and the secrets they keep. Hanna's desperate for a very personal session with her gym trainer. Emily is number one on Santa's naughty list. Aria's old flame from Iceland is about to land her in hot water. And Spencer's resorting to some backhanded tactics to get what she wants.