Johan Daas, an elderly man residing in a rural village near Antwerp, assumes responsibility for his two-year-old grandson Nello following his daughter's death in the Ardennes. Despite significant poverty and his own advanced age, Johan provides care within their meticulously maintained, modest mud hut. His mobility is limited by a disability requiring a walking stick. To sustain themselves, he and Nello deliver milk using a cart. During one route, they encounter a severely injured, abandoned dog. Despite their hardship, Johan consents to rescue it. The dog recovers, is named Patrasche, and becomes an integral household member, assisting with deliveries.

Johan consistently supports Nello's artistic aspirations, recognizing and encouraging the boy's drawing talent inspired by Peter Paul Rubens, even amidst ongoing financial precarity. He exhibits a patient and understanding demeanor, particularly regarding Nello's friendship with Aloise, a girl from a wealthier family. Their livelihood faces pressure from a landlord demanding increased rent. Johan's health deteriorates over time, culminating in his death while seated outdoors. This occurs before the narrative's conclusion and directly results in Nello and Patrasche's eviction from their home due to unpaid rent, forcing them into winter homelessness.

In one film adaptation, Johan receives a deathbed promise from his daughter to care for Nello. The opposing landlord is named Stevens, and Johan actively defends Nello against accusations of arson after a fire at the Cogez mill. His death scene in this version portrays a peaceful passing as Nello attempts to show him a drawing. Across adaptations, Johan's character subtly develops from a pragmatic survivor facing hardship to reveal compassion through rescuing Patrasche and steadfastly encouraging Nello's art. His relationship with Nello is characterized by mutual devotion; his final moments reflect concern for the boy's future well-being. His death serves as the catalyst for the subsequent events involving Nello and Patrasche.