Has anyone seen Jessica Jenkins?

"Jessica Jenkins is missing...Jessica Jenkins has always thought she was a perfectly ordinary girl, until the day that part of her arm vanishes in the middle of a Geography lesson! Her best friend Izzy is determined to help Jessica realise what a great opportunity the power to turn invisible could be, but where has her new ability come from? Does this mean she's a superhero? And, when her friends are threatened, can Jessica use her superpower to...