When one of their tightly-knit group mysteriously disappears, four high school girls find their friendship difficult to maintain when they begin receiving taunting messages from someone who seems to know everything about their past and present secrets.

New revelations and betrayals push the girls to their limits

Struggling to return to normalcy after surviving Alison's attempt to kill them, Spencer, Aria, Emily and Hanna endure a series of disasters before realizing that they are being stalked by a new "A" who knows all of their secrets

Deciding to come clean about a terrible mistake they committed during spring break, high school seniors Aria, Emily, Hanna, and Spencer hope to end the blackmail of a ruthless stalker who retaliates by plotting a murderous revenge

The girls face dangerous consequences as secrets begin to unravel.