Is it possible to forget that you've committed a murder? When Cassie Fitzgerald was at school in the late 90s, she and her friends killed a fellow student. Almost twenty years later, Cassie is a happily married mother who loves her job--as a police officer. She closely guards the secret she has all but erased from her memory. One day her husband finally persuades her to go to a school reunion. Cassie catches up with her high-achieving old friends...

When her colleague and close friend is murdered, high-school English teacher Clare chronicles her suspicions about the case in her diary until one day she discovers a sinister message in it and fears that a dark story has come to terrifying life.