Donald and his nephews are at a dude ranch, but there's a horse thief at the surroundings. As the ranch owner has to go to a meeting, Donald guards the horses and promises that if one gets lost, he will buy a replacement.
Ten minutes later, a man arrives telling he comes from the meeting and the ranch owner asked for the horses. When he is leaving with the horses, Dewey asks Donald how far is the meeting, and he answers 40 km, to which all three nephews signal that the owner couldn't arrive and send the man in 10 minutes. Donald cannot follow him as the fouyr wheels of the 313 were flattened by the thief.
The thief returns disguised in shades and a fake mustache, and sells three horses to Donald, who doesn't recognise him and buys them to fulfill his promise. When the nephews go to see the new horses in the corral, they have disappeared. The disguised thief returns to sell three brown horses.
Donald hears horse steps upstairs and finds the horses leaving through a door, but it turns it was a projector image and a speaker, as a diversionary tactic. Huey, Dewey, and Louie call Donald back down to tell him the brown horses disappeared. The thief then comes selling three spotted horses.
Dewey gets an idea from the horses being spotted, as there is a spotted horse disguise in the house, so the kids use it and check the other horses. A whistle comes from the haystack and the horses untie themselves to follow it, and the nephews do the same to know what happens. Then they reach a secret passageway in the haystack and follow the thief as if they were trained. Then, in a hidden place, he paints them, this time in blue.
Donald finds the horses have been stolen again, and his nephews have disappeared too. When the thief arrives selling blue horses, Donald gets fed and threatens with shooting him, so he escapes back to his hideout and packs to begin in other ranch, but the disguised kids kick him into one of his own paint barrels.
Meanwhile, the ranch owner returns and Donald tells him what happened, when the nephews arrive and Dewey, with the thief's disguise, offers to sell four horses, to which Donald says there's only three. Huey takes the thief out of the barrel telling he's the fourth one, somewhat uneasy because he doesn't like to be a horse.