Most people think Rebecca Yallop is simply a very tall young girl with a longish face, but her brother, Kevin, knows the truth: Rebecca's a horse!
One wayward wish made during a visit to the Amazing Beryl's Make-a-Wish tent at the Dingaling Brothers Big Top, Flying Monkeys and Sea Slug Circus Extravaganza and now Rebecca's a 300-kilogram horse, trying desperately to behave like a normal 12-year-old girl. It's hard, though, when you have to use your mouth to make your bed and you have trouble fitting into your mum's VW beetle. Rebecca and Kevin have to find the Amazing Beryl so she can turn Rebecca back in to a girl.
When they discover Beryl is spending a year with the mystical, one-legged Sherpas of the Upper Langtang Valley in Nepal, Rebecca thinks she has no hope of becoming a girl again. Then she learns that her favourite television show, Saddle Soar, is holding open auditions and Rebecca has a chance to not just earn the money to pay for the trip, but to become famous...