May Grover has bad news. Her pony, Macaroni, has a sore foot, and she can't ride him until he's better. But May has the perfect solution: She can help her father train his new student, a pony named Zeus. Soon May is so busy training the smart new pony that Macaroni gets jealous. And May starts to feel left out herself when her best friends in the Pony Tails seem to forget about her!