Katie is delighted to be selected as the captain for Paddock Grove's under-14 equestrian team in the county competition. She and her horse, Sheriff, are a great duo and she's excited to prove this in the arena and on the cross country course. But when the competition starts, strange things start to go wrong around the stables. At first Katie suspects mean-girl Megan who's been banned from competing, but as the 'pranks' start to escalate, she starts to believe that someone on one of the other teams might be trying to sabotage Paddock Grove's chances by playing tricks on their team captain. If she can't find the culprit, they might run her and Sheriff out of the competition altogether...