1. Pilot

Aria Montgomery, Emily Fields, Hanna Marin, and Spencer Hastings grow distant after the disappearance of their clique leader, Alison DiLaurentis. A year later, they begin receiving anonymous messages from a figure known as "A", who threatens to expose their secrets. Aria returns from a year in Iceland and knows about her father Byron's affair, which her mother does not yet know about. She also learns that her English teacher, Ezra Fitz, is the man she met and kissed at a bar the previous day. Hanna has become the school's "it" girl but indulges in shoplifting; when she is caught, her mother Ashley sleeps with Detective Wilden to secure her release.

Spencer develops feelings for her sister Melissa's fiancé, Wren Kingston, and Emily befriends Maya St. Germain, who has moved into Alison's former home. The friends initially suspect Alison of being "A", but her body is later discovered. At the funeral, they see Jenna Marshall, a classmate blinded in an incident involving the girls and Alison, and soon receive another message: "I'm still here bitches. And I know everything. –A."