If only you knew then what you know now ... Imagine if you could meet your 21-year-old self - would you recognise her? And what advice would you give? Wear sunscreen! Back away from those PVC trousers? DON'T give that idiot your phone number? Lemon juice won't bleach your hair - it just attracts wasps ... For Charlotte Merryweather, there's no need to imagine. She's about to find out for real. With surprising consequences.