When twenty-one-year-old social media star Chelsea Dawson disappears, Seneca, Maddox, Aerin, and Madison, noticing that she looks exactly like Aerin's murdered sister, Helena, investigate, determined to find the connection.

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.

Former best friends Emily, Aria, Hanna, and Spencer continue to live in fear as they struggle to keep hidden even more secrets and someone new begins stalking them via their cell phones.

After their friend who has been missing for more than three years turns up dead, four former best friends continue to receive frightening messages from someone who knows damaging secrets about them.

Seventeen-year-old Sutton Mercer watches from the afterlife as her long-lost twin sister, Emma Paxton, continues to pretend to be her in order to identify Sutton's killer.

After surviving their latest encounter with A, high school seniors Aria, Emily, Spencer, and Hanna must try to convince the police that the real A is still on the loose, all while trying to stay alive.

A tale set in the seventh grade in the weeks leading up to Ali's murder reveals her plots against Emily, Hanna, Aria and Spencer, as well as a dark secret that has the potential to destroy everything.