Once little Willy learns that his grandfather is sick in bed because he has no reason to live. Little Willy and his grandfather make their home on a potato farm in Wyoming, and although the work can be back breaking, it is also a lot of fun, especially when Grandfather plays with Willy. Now with Grandfather too depressed to speak, much less get out of bed, Willy and his loyal dog, Searchlight, have to harvest the crop themselves. They need to rent a horse, but when Willy looks in the strongbox for money, he discovers that they are broke. The problem is solved when Searchlight takes up the harness in her mouth. Willy and Searchlight are able to plow the fields and harvest the potatoes, but when they present Grandfather the money earned from its sale, Willy finds out that his Grandfather is still depressed.

Willy discovers that Grandfather needs 500 dollars to pay off 10 years worth of back taxes on the farm, or they will lose it. In a daring plan, Willy enters the National Dogsled Race, and stakes everything on the wild hope that he can outrun the best dogsled racers in the country including the legendary Indian, Stone Fox. The fast-paced, thoroughly engrossing description of the race reaches a sudden, tragic climax when Searchlight dies just before the finish line. In a moving end, Stone Fox understands that Willy and Searchlight are the true winners and allows Willy to carry Searchlight across the finish line and collect the prize.