Mystery of the Midnight Rider - Nancy Drew Diaries #3

Dear Diary,

Who would want to harm a horse? I kept asking myself that question while watching the beautiful jumpers at the annual River Heights Horse Show. The top riders from all over the country are here, and one of them, Payton Evans, is a close friend of Ned's family. She's been training for years, and Ned said she might even make the Olympic team. But just when Payton was supposed to compete in this show, everthing went horribly wrong: Her horse, Midnight, tested positive for drugs! What kind of person would ever give drugs to a horse? And why?