Alison, Aria, Emily, Hanna and Spencer were best friends, until Alison disappeared. Three years later, the remaining girls, now juniors at Rosewood Day, are leading separate, but charmed lives. But in Rosewood, appearances are deceiving, and when the girls start receiving mysterious texts signed by someone named A, the past threatens to ruin their perfect present. A claims to know all of their secrets—but who is A? How much does A really know? And what can four pretty little liars do to protect themselves from the truth?