Pretty Little Liars follows four high school girls—Spencer Hastings, Hanna Marin, Aria Montgomery, and Emily Fields—whose clique falls apart after the mysterious disappearance of their queen bee leader, Alison DiLaurentis. Three years later, the four girls start receiving strange text messages from someone who refers to themselves as "A." The texts threaten to reveal the girls' deepest secrets—things they thought only Alison knew.