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.

"Emily's been shipped off to Iowa to live with her ћuberconservative 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 their friend who has been missing for more than three years turns up dead, four former best friends continue to receive frightening messages from someone who knows damaging secrets about them.

"It's spring break, and the pretty little liars are trading in Rosewood for a cruise vacation. They want nothing more than to sail into the tropical sunset and leave their troubles behind for one blissful week. But where Emily, Aria, Spencer, and Hanna go, A goes, too. From scuba diving to tanning on the upper deck, A is there, soaking up all their new secrets. Emily is smooching a stowaway. Aria's treasure-hunting partner is a little too interested...

"Ava, Caitlin, Mackenzie, Julie, and Parker are all driven to be perfect--no matter the cost. At first the girls think they have nothing in common, until they discover that they all hate the same person: handsome womanizer Nolan Hotchkiss, who's done things to hurt each of them. They come up with the perfect plan to murder Nolan--jokingly, of course. They'd never actually go through with it. But when Nolan turns up dead in the exact way they'd discussed,...

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.

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.

Emma tracks down the final clues that will help her solve the mystery of her identical twin's murder.

"Four teens who met on an online cold-case solving forum attempt to solve another teen's murder"--

Aria's love life is on the Fitz--ahem, fritz. Emily's exploring her wild side. Hanna's kissing the enemy. And someone from Spencer's past--someone she never thought she'd see again--is back to haunt her. But none of that compares to what these pretty little liars did on their last spring break. It's their darkest secret yet. And guess who else knows?