Sara Shepard 
Unbelievable 
Number 4 in series

In Rosewood, where the air smells like apples and Chanel No. 5, nothing is as it seems. Five best friends once shared everything – even their deepest, darkest secrets. Back then for Aria, Spencer, Hanna, and Emily it was a dream come true . . . until Alison, the most beautiful of them all, suddenly vanished.
Now someone named A has turned their charmed lives into a living nightmare. With A»s threats turning dangerous and Ali»s killer still on the loose, the girls must uncover the truth, but will it bring an end to the horror . . . or is this just the beginning?