Former best friends Hanna, Aria, Spencer, and Emily, who lost their best friend and leader, Alison, years ago when she disappeared, find themselves in grave danger when they pursue the truth about Alison.

Seventeen-year-old Margaret "Cuckoo" Clark keeps a journal detailing the trials and tribulations of high school life as she and her close-knit group of outcast friends try to break down the barriers between their school's "warring nations."

In chapters that alternate between the past and the present, Cat slowly recalls her life before she and her classmates were trapped inside School, where half of them are mutating, everyone is fearful, and self-destruction seems to be the only means of escape.

When a teenaged girl with a bad reputation is murdered in New York City's Central Park after a party, her childhood friend is determined to solve the mystery of who caused her death.

Sixteen-year old Jessie, still grieving over her mother's death, must move from Chicago to "The Valley," with a new stepfamily but no new friends until an anonymous fellow student emails and offers to help her navigate the school's treacherous social waters.

The stalker's identity has finally been revealed, but Spencer, Emily, Hanna and Aria are bound to repeat the past, and continue to be bad.

A studious girl and a quiet, straight-A boy start a controversial podcast together that challenges their courage and forces them to confront issues in the form of backlash and censorship.

After high school juniors Spencer, Emily, Hanna, and Aria think they have seen Ali, their missing and presumed dead friend, they pursue clues from a mysterious stalker, trying to find out if she is still alive.

After seventeen-year-olds Chole and Shara, Chole's rival for valedictorian, kiss, Shara vanishes leaving Chole and two boys, who are also enamored with Shara, to follow the trail of clues she left behind, but during the search, Chloe starts to suspect there might be more to Shara and her small Alabama town than she thought.

High school senior Paige knows there is so much more to life after high school, but is it so terrible to want everything to stay the same forever? What happens after happily ever after? It's senior year, and Paige Hancock is finally living her best life. She has a fun summer job, great friends, and a super charming boyfriend who totally gets her. But senior year also means big decisions. Weighing "the rest of her life," Paige feels her anxiety begin...