While on vacation at a dude ranch, the Casebusters chase a horse thief Sean and Brian Quinn can’t think of anywhere cooler than the Austin Dude Ranch. Although neither has ever ridden a horse, they’re positive that playing cowboy is going to become their favorite pastime. But before they can learn to rope and ride, they’re going to have to practice their other favorite hobby: solving mysteries.   A racehorse has been stolen from the neighboring farm, and the ranch’s owners think that their horses may be the next to disappear. To find the missing pony, Brian and Sean will have to confront something even more scary than horse thieves: the ghost of the crazy old gold prospector who is said to haunt a nearby abandoned mine. Whether the culprit is living or dead, Brian and Sean must catch him faster than they can say, “Giddy-up!”