On a sunny morning, Alison, her half-sister Kitty and friend Vanessa went to school. And an hour later there was a terrible car accident in which Alison miraculously survived, but Vanessa died, and Kitty was left severely disabled.Now, fifteen years later, Kitty still cannot speak and suffers from memory lapses, and art teacher Alison leads a quiet life and tries in vain to forget what happened that morning.However, when Alison, despite her fears, accepts an offer to teach courses for prisoners in a local prison, something strange and frightening begins to happen ... p>She and her sister are being followed and threatened with anonymous notes.Someone lurking in the shadows is waiting and preparing to strike. Someone who knows well what really happened many years ago…