Continuations of Ben and Dixie Darby's adventures bud on a day at the races in Boise, flower into the kids' first real experiences with thoroughbreds and racing after Ben foolishly buys a troublesome racing stallion, Peck, at a bargain price of $300. A chance for the unpromising Peck comes when an Arizona racing man, Andy Blair, comes to the Darby's Tack Ranch just outside Boise, to buy a colt- a midnight colt-sired by the famous wild stallion Black King. The midnight colt gets sick and dies. Blair decides to gamble on Peck and Ben and Dixie have the opportunity to go with him to Arizona, calm Peck into a more ridable animal, race him, win him, and discover, through a mix-up in pedigrees that Peck too, is a midnight colt, and hence worth a lot of money. In order to get to the horsey stuff wherein lies the value of the book, the reader has to stomach such things as Ben's glib and unpunished money spending, the relatively easy thing it seems to be for children to go off racing horses around the country-side. But there's the market for westerns that waxes ever strong and unfailing.