In rural Scotland, after the body of a sheep is found mangled, shepherds Sam'l Thornton, Long Kirby, MacKenzie and Ferguson come to Adam M'Adam's home to accuse his mongrel dog, Red Wull, of the killing. When the men demand the execution of M'Adam's beloved canine, the wily M'Adam plays on their sympathy by conjoining his fate to that of his dog, thus gulling them into withdrawing their demand. After the men leave, M'Adam's son Davie goes to town and visits Angus MacIvor's shop to admire a violin in the window. Davie, who lost his cherished mother, longs to recover the love of music that she instilled in him, and so haggles with MacIvor over the price of the instrument. Upon returning home with his newly purchased violin, Davie is chastised by his father, who is bedeviled by drink and by memories of his long-lost wife. After M'Adam insists that Davie return the violin in the morning, the boy seeks solace at Kenmuir, the neighboring ranch owned by James and Elizabeth Moore. In Mrs. Moore, Davie finds the love he once shared with his own mother, and consoles himself playing the violin as Mrs. Moore accompanies him on the piano. When the Moores' sheep dog Bob follows Davie home, the cantankerous M'Adam trains his rifle on the animal, and Davie strikes his father to queer his aim. In punishment, M'Adam beats Davie, who then returns to the Moore ranch, where sixteen-year-old Maggie treats his wounds. Weeks later, Mrs. Moore suffers mortal injuries while giving birth to a baby girl, and as she clings to life, she calls for Davie. When the boy finally appears, Mrs. Moore gives him her violin and then peacefully passes away to the strains of Davie's music. While Davie attends Mrs. Moore's funeral during a downpour, M'Adam stays home, opens the violin case and finds a photograph of his late wife. M'Adam prays to the image of his wife to make him a better parent, and when Davie returns home, he apologizes to the boy and tries to reconcile with him. However, when Davie plays the violin as a tribute to his mother, his father becomes enraged and smashes the instrument. After denouncing his father, Davie vows never to return home again and takes refuge at the Moores'. The week before the sheep dog herding trials, M'Adam, who won the trophy with Red Wull the previous year, insults Moore, his major competitor. Stung, Moore withdraws his dog Bob from the contest. Maggie's new responsibilities as woman of the house, meanwhile, has matured her into womanhood, thus attracting Davie's attention. On the day of the sheep dog championship trials, Bob whimpers at being excluded while Red Wull bullies his flock into submission and wins the trophy to the jeers of the crowd. Later, when sheering time arrives, the farmers refuse to help the irascible M'Adam fleece his flock, but Moore defends his neighbor. One wintry day, Bob leads Maggie and Davie to a helpless newborn lamb, and after adopting the animal, Davie kisses Maggie. A year passes, and as the annual sheep dog trials approach, M'Adam goads the farmers at the pub into betting against Red Wull. Just then, Ferguson enters and accuses Red Wull of killing his sheep. When a fight breaks out, M'Adam is arrested and brought to trial. To avoid losing the championship and thus having to pay off his wagers, M'Adam persuades the judge to sentence him to jail for fourteen days, but the bettors thwart his plan by paying his fine. On the eve of the sheep dog trials, after Moore traces Bob's championship lineage, Davie reveals that his father reared Red Wull from the time he was an abused mongrel pup. The regulations of the contest state that the cup permanently belongs to any dog that wins three times in a row, and because Red Wull has won the two previous years, Davie knows that M'Adam's heart will be broken if he loses this year and is forced to forfeit the trophy. At the trials, Moore designates Davie to be Bob's handler, and in spite of himself, M'Adam quietly roots for his son. After Bob wins the event, M'Adam removes the trophy from his mantel and carries it to Kenmuir. At Kenmuir, meanwhile, several herders have notified Moore that they found the carcass of a sheep and spotted Bob nearby. As Moore goes in search of his dog, he encounters M'Adam in the pasture. Summoned by his master's call, Bob appears, his paws bloodied. Assuming that Bob killed the sheep, Moore is about to shoot Bob when the blood-thirsty call of another dog is heard and they find Red Wull hovering over a dead sheep. With a heavy heart, M'Adam returns home with his dog, and after bidding him a fond farewell, walks into the pasture and shoots him. M'Adam then takes his last prized possession, the trophy, to present to the Moores. At the Moore house, M'Adam is warmly greeted and discovers that Davie has arranged for Bob to be disqualified from the contest because he was handled by someone other than his owner. Davie then tells his father that he plans to marry Maggie, and Maggie invites him to live with them. M'Adam sputters in protest and asks Davie to play a tune for them. After drinking a toast, Davie begins to play "Auld Lang Syne," and as they all join in song, Bob wags his tail.