Everyone has something to hide—especially high school juniors Spencer Aria Emily and Hanna. Spencer covets her sisters boyfriend. Arias fantasizing about her English teacher. Emilys crushing on the new girl at school. And Hanna uses some ugly tricks to stay beautiful. But theyve all kept an even bigger secret since their friend Alison vanished. How do I know? Because I know everything about the bad girls they were and the naughty girls they are now. And guess what? Im telling.