When foul play is suspected at the horse ranch, girls join Barbie? to become super sleuths on horseback to solve the mysterious disappearance of the prize horse belonging to Teresa?, before the big riding competition gets underway. Prior to starting the adventure, girls sharpen their riding skills by trotting, herding and jumping at the practice ring. They get their horses ready by brushing their manes and feeding them carrots, apples or sugar cubes. Girls untangle puzzles and jump over obstacles like logs and fences, as they guide Barbie? on the trails. Girls help Barbie? search for clues hidden in an abandoned campsite, an old town, a cave and other exciting locales. Using the clues to uncover the mystery, girls find and return the prize horse in time for the show.