One day, the kind-hearted boy Lucas (Jonah Hauer-King) meets a lonely puppy in an abandoned building. Although Lucas's mother forbids him from keeping pets, Lucas, who can't bear to see the puppy left unattended, still brings the puppy home and names it Bella, thus Bella becomes a new member of the Lucas family.
One day, Lucas' mother took Bella to the Veterans Hospital to see a doctor. Who knew that Bella not only did not cause her trouble, but also brought happiness to the unhappy patients in the hospital. Soon, Bella became a popular star in the hospital. An accident forced Lucas to foster Bella in a friend's house, and Bella decided to run away from home and reunite with her master through her own courage and wisdom.
