The eldest cousin and natural leader of the group, Julian is diplomatic and fair, often strategizing and mediating between his younger siblings and George during their adventures.

Julian's younger brother, known for his quick thinking and bravery, often playing a critical role in deciphering clues and aiding in the group's daring plans.

The youngest cousin who embodies traditional femininity and is often timid, yet proves to be insightful and resourceful in crucial moments of the group's escapades.

George's loyal dog serves as both protector and reliable companion, contributing to the group's success with his keen senses and alertness to danger.

George's father, a stern and academically absorbed character whose actions inadvertently drive much of the plot, showcasing his impatience and lack of awareness of the children’s activities.

A nurturing and welcoming figure providing warmth and stability, Aunt Fanny often mediates between the children and Uncle Quentin while supporting George's friendships.

A group of armed men seeking treasure, representing a collective force of external conflict, whose underestimation of the children sets up the central conflict of the story.