"Why does it matter whether I am a boy or a girl? But it does. It really, really matters." When Alex was born, the doctors described him as "sexually ambiguous", with both male and female reproductive organs. For the last fourteen years his parents have raised Alex as a boy. They dressed him in boys' clothes, sent him to a boys' school and gave him medication to help regulate his hormones. But last night at dinner, Alex made an announcement, three words that would change everything: "I'm a girl". And when Alex sets about changing her life—her wardrobe, her school, her entire identity—no one knows how to react, least of all her parents.