Jehan Daas, known as Grandpa, is an elderly man living in a small Flemish village near Antwerp during the 19th century. He becomes the sole guardian of his young grandson Nello after the boy's mother dies when Nello is approximately two years old. They share a modest shack on land owned by a local landowner.

Jehan earns a meager living collecting milk from nearby farms and delivering it by cart to customers in Antwerp each dawn. This work is strenuous due to his advanced age and physical limitations. His life changes when he and Nello find an abused and nearly dead dog named Patrasche abandoned on the road. Despite their poverty, Jehan insists on nursing the dog back to health, instructing Nello to care for it.

Jehan exhibits profound kindness, humility, and a strong sense of responsibility. He deeply regrets his inability to provide Nello with financial security or opportunities, yet actively supports the boy's artistic aspirations within his means. He demonstrates integrity by honoring agreements, such as paying a significant sum to Patrasche's former abusive owner to secure the dog's freedom, straining their difficult circumstances.

To support Nello and cover Patrasche's costs, Jehan secretly takes on extra labor. This additional exertion, combined with his age, inadequate nutrition, and lack of medicine, causes a severe health decline. He eventually dies, leaving Nello orphaned and vulnerable to false accusations from villagers, including being wrongly blamed for a windmill fire. His death results in Nello and Patrasche's eviction from their home.

Throughout his life, Jehan serves as Nello's primary emotional anchor and moral guide. Their relationship extends beyond familial duty, reflecting a deep bond of mutual affection and shared resilience against hardship. His actions consistently prioritize Nello's well-being and happiness, even at significant personal cost.