Jack has finally found a home and a purpose on a farm, where he keeps a flock of sheep safe from coyotes and helps train young pups to do the same. But when two sheep disappear in broad daylight, Jack doesn't know what happened to them. Was it his fault? Is he just getting too old for this job? Still, he's determined not to disappoint his boy, Luke, who thinks that Jack is the smartest and fastest dog around. Then Jack and Luke discover that the animal threatening their farm is far more dangerous than any coyote: it's a rabid wolf. Jack knows that he must gather the courage and strength to protect the ones he loves most—but can an old dog learn new tricks?