"Fiendishly addictive". (Guardian). Your best friend isn't who you think she is. You've been friends since university, when you became the people you are today. You don't see each other enough but when you do it's as if you've never been apart. She's one of the family. You would trust her with your life, your children, your husband. And when your daughter is rushed to hospital, you're grateful that she's stepping in at home, looking after things. But your best friend isn't who you think she is. You're about to find out just how wrong you were.