Xanthe Fox can't wait to turn thirteen, but as the big day arrives her world starts to fall apart. Set-up at school for something she didn't do, it seems her age old enemy, Kelly, is making trouble for her ... and as things escalate, even her best friend Saul starts to doubt her innocence. With the school threatening to expel her, and mysterious glowing Xs appearing in front of her eyes, Xanthe turns to Grandma Alice for help. But what the old lady tells her will change Xanthe's life for ever...