In a rural village outside Antwerp in nineteenth century Belgium, Nello Dass, a poor orphan who helps his infirm grandfather Jehan deliver milk, dreams of becoming an artist like his idol, Peter Paul Rubens. One day, a drunken peddler brutally beats his dog and leaves him to die by the side of the road. While returning from their milk route, Nello and Jehan come upon the nearly dead dog and Nello begs to bring the dog home and nurse him back to health. Jehan reluctantly agrees, and Nello decides to name the canine Patrasche, after Rubens' dog. Alois Cogez, the miller's little daughter, gives Nello a bone for his dog, but the Dass family is so poor that grandfather insists on flavoring the soup with it first. Alois' father, a prosperous businessman, disapproves of his daughter's friendship with the "ragamuffin" Nello. Under Nello's loving care, Patrasche thrives and gradually loses his wariness of humans. While delivering milk to Antwerp one day, Jehan stops at the diamond mart, intending to apprentice Nello to a diamond merchant he knows there. The merchant has drowned, however, and the cold-hearted merchant to whom Jehan speaks refuses to help the boy. In his grandfather's absence, Nello draws a sketch of a fountain in the town square, attracting the attention of artist Piet Van Gelder. The gruff Piet, frustrated by his own work, at first scoffs at the boy's ambition and then relents and gives him advice on technique. Concerned about Nello's future, the practical Jehan admonishes the boy to give up his dream of becoming an artist. That night, the cold-hearted landlord comes to collect the rent and offers to buy Jehan's brass bed, the last remnant of his happy marriage, but Jehan refuses his offer. The next morning, Patrasche eagerly climbs into the milk cart harness and Jehan, hobbled by old age and pain, stays behind at home. In Antwerp, Nello visits the cathedral that houses Rubens' triptych of the crucifixion, but is turned away by the priest for lack of the one franc viewing fee. When he leaves the cathedral, Nello finds the peddler trying to steal Patrasche, but Piet comes to their rescue. In his skirmish with the peddler, Nello injures his hand and Piet takes him to his studio for treatment. There, Nello tells Piet of his plans to enter a painting in the children's Christmas contest. When the boy questions him about his paintings, Piet becomes angry and throws him out after giving him some pens and drawing paper. Corrie, Piet's long-suffering model, tries to comfort the boy. Soon after, the peddler returns to beat Nello and steal Patrasche. When Alois sees the peddler dragging the reluctant dog, she calls to her father to come to Nello's defense. Enraged by the peddler's brutality, Cogez turns the growling Patrasche loose, and while fleeing the angry dog, the peddler runs into a windmill blade and dies. Alarmed, Cogez orders Nello to leave the mill and never return. Finally recognizing Nello's talent, Jehan gives the boy his few remaining possessions to sell so that he can buy some art supplies. In Antwerp, Nello visits Piet's studio, where Piet insults Corrie by declaring he will never marry her. After Corrie runs crying from the room, Piet tutors Nello on how to blend colors and gives him some paints. When Corrie returns, Piet confesses his love to her and they embrace. With his new paints, Nello decides to draw his grandfather and his dog, but once the portrait is finished, Nello discovers that the old man has died while posing in his chair. With his last coins, Nello pays for his grandfather's funeral. Having lost all his milk customers, Nello is unable to pay the rent and the landlord barters Jehan's beloved bed for one month's reprieve. Now destitute, Nello's one last hope is to win the contest money. Cold and hungry, Nello begs for food for Patrasche and then hurries to hear the result of the contest. After his painting loses, Nello, desperate, goes to Alois and pleads with her to take care of Patrasche because he can no longer afford to feed him. After Nello tearfully departs, Patrasche whines at the door for his master. Soon after, Alois' parents return home and, apprised of the situation, Cogez decides to find Nello and offer him an apprenticeship. Just then, Piet knocks at the door and, holding Nello's painting, declares that he wants to apprentice the boy. Alois then suggests that Patrasche will lead them to the missing Nello. On Christmas Eve, in the midst of a snowstorm, Nello visits the cathedral, and the priest relents and allows him to view the painting at last. As Nello gazes skyward toward the triptych, Patrasche, by Alois, Piet and Corrie run into the cathedral and hug him.