Prospero is a twelve-year-old boy who has recently lost his mother and taken on the immense responsibility of caring for his younger brother, Boniface. Resourceful and highly protective, he runs away to Venice to prevent his aunt and uncle from separating them. He acts as the moral compass of the orphaned gang they join, worrying about their safety and criminal activities.

Boniface is a five-year-old boy who is deeply attached to his older brother, Prospero. He is naive, playful, and views their harsh life on the streets of Venice as a grand adventure. Readily trusting and easily fascinated by the older gang members, he idolizes their leader and struggles to understand the danger of their situation.

Scipio is the self-proclaimed leader of the youth gang, donning a plague doctor mask and high-heeled boots to appear older and more authoritative. He provides for the other children by bringing them stolen goods to fence. He longs for independence and the power of adulthood, keeping aspects of his personal life strictly separate from the rest of the group.

Victor is a private detective living and working in Venice, distinguished by his love for disguises and his two pet tortoises. Hired to track down the missing Hartlieb brothers, he approaches the case with a blend of professional duty and personal sympathy. He retains a childlike sense of adventure and playfulness, which allows him to relate to the children he investigates.

Ernesto Barbarossa is a red-bearded antique dealer who operates a shop called Souvenirs of Venice. He acts as a fence for the gang, purchasing their stolen goods at a fraction of their value. He is shrewd, manipulative, and entirely motivated by profit, frequently attempting to cheat the children while using them to connect with wealthy clients.

Esther is Prospero and Boniface's wealthy, privileged aunt from Hamburg. Following her sister's death, she decides she only wants to adopt young Boniface, planning to send Prospero away to boarding school. She views children more as possessions than individuals, prioritizing her own desires over her nephews' well-being.

Max is Esther's husband, a wealthy man who openly dislikes children. He goes along with his wife's plan to adopt Boniface and discard Prospero, displaying a total lack of empathy for the boys' loss and their sibling bond. He views children as loud, dirty, and largely interchangeable.

Hornet is the sole girl in the youth gang, acting as a grounded and maternal figure for the others. She manages the group's money and supplies, surrounding herself with stacks of books that she reads to the others at night. Fiercely protective of her chosen family, she is deeply loyal and skeptical of unnecessary risks.

Riccio is a scrappy and excitable member of the gang, known for his love of comic books and stuffed animals. He acts as one of the primary scouts, surveying potential marks for burglaries. He revels in the freedom of childhood, strongly distrusts adults, and is deeply devoted to the family the gang has built.

Mosca is a mechanically minded member of the youth gang, characterized by his toolbox and fishing rods. He acts as the eyes of the group alongside Riccio, staking out locations and managing the technical aspects of their survival. Though quiet and focused on repairs, he is deeply attached to the younger members of the group.

The Conte is an aged, mysterious client who hires the gang to steal a specific wooden wing. He operates through intermediaries and secret messages, refusing to deal directly with Ernesto Barbarossa. He is singularly focused on obtaining the missing piece of a legendary carousel.

The Contessa is the Conte's sister, assisting him in his quest to obtain the wooden wing. She helps coordinate the exchange with the gang and shares her brother's deep desire to access the legendary carousel, protecting their secrecy fiercely.

Ida Spavento is an adventurous photographer who lives alone in a large house in Venice. Having grown up as an orphan herself, she immediately sympathizes with the youth gang instead of calling the police. She is a compassionate adult who retains a childlike curiosity and a love for local legends.

Dottor Massimo is the wealthy owner of the Stella movie theater and several other properties in Venice. He is a rigid, formal man who views the youth of the city as a nuisance. He expects strict discipline and dismisses emotional attachments, prioritizing his business and social standing.

Lucia is Ida Spavento's housekeeper. She inadvertently provides Riccio with reconnaissance information when he helps her with her groceries. She is an accommodating presence in Ida's home, assisting in caring for the house.

Giaco is the husband of Ida's housekeeper, Lucia. He assists Ida with navigating her motorboat through the Venetian canals, providing transportation and support during her adventurous outings.

Lando is one of Victor Getz's pet tortoises, rescued from a previous case. He provides Victor with quiet companionship in his office, reflecting the detective's softer side.

Paula is Victor Getz's other pet tortoise. She occasionally falls ill and requires veterinary care, demonstrating Victor's gentle nature and commitment to his dependents.