Among the mega mansions and perfectly manicured hedges of Rosewood, Pennsylvania, everyone has something to hide - especially four very pretty little liars. High school juniors Spencer, Hanna, Aria, and Emily have been keeping secrets ever since their best friend, Alison DiLaurentis, disappeared three years ago. But when the girls begin receiving threatening notes from someone named 'A,' their secrets - the big ones, the little ones, even the long-buried ones - no longer seem so safe.