From the moment Katy sees Genevieve's beautiful face staring at her from a window, her life will never be the same. Wherever Katy turns, Genevieve is there - at school, with Katy's friends, and worst of all, in Katy's hot new boyfriend's life.

But Genevieve has a menacing side, a dangerous side, a threatening side that she only reveals to Katy: I'm your worst nightmare.

When Genevieve's behaviour becomes increasingly twisted, Katy delves into the girl's past, with the help of her best friend Luke. Nothing prepares her for the dark truths that she discovers, or the new romance she finds along the way. Is Genevieve a troubled girl with a difficult childhood? Or is the truth unearthly and much more frightening?

Who is the real Genevieve?

What are her secrets?

Why is she determined to destroy Katy's life?

A rich, twisting thriller of friendship, love and evil that you'll find impossible to put down.