Every holiday, Emma loves helping her grandma Dolly at her animal sanctuary. At home she isn't even allowed a guinea pig. While she's there, Emma's grandma buys her Mississippi, the beloved horse of an old friend, Mr Clipperbush, who has passed away. Emma can't believe her luck - a horse of her own. But suddenly, there's trouble. Mr Clipperbush's long-lost nephew wants the horse back - and will stop at nothing to get his way. What can Emma do? Saving Mississippi means everything...