Maia is a wealthy, orphaned girl sent from England to live with distant relatives in the Amazon basin. Rather than fearing the jungle like her classmates, she enthusiastically studies the region and approaches her new life with courage. She possesses a natural talent for music and a sincere desire to form genuine connections with the people she meets.

Miss Minton is Maia's formidable new governess. While her severe exterior and dark spectacles initially intimidate others, she hides a deep passion for natural exploration. She fiercely protects Maia and encourages her young pupil's curiosity about the rainforest.

Finn is a resourceful boy who travels the Brazilian rivers alone in his boat. As the son of a British naturalist and an Indigenous Xanti mother, he possesses extensive survival skills and medicinal knowledge. He actively avoids private investigators who wish to drag him back to a restrictive aristocratic life in England.

Clovis is an orphaned child actor working for a traveling theater troupe called The Pilgrim Players. He suffers from stage fright and deeply misses his former foster mother in England. He detests the hot climate and finds comfort in interacting with fellow British travelers.

Mr. Clifford Carter is Maia's distant relative who agrees to host her in Brazil strictly to collect her monthly financial allowance. He runs a failing rubber plantation and treats his local workers with severe cruelty. He distracts himself from his financial ruin by obsessively collecting glass eyes.

Mrs. Carter is the matriarch of the Carter household. She maintains a paranoid hatred of the rainforest environment, constantly dousing her home in toxic chemical pesticides. She spoils her daughters while treating Maia with calculated neglect.

Gwendolyn is one of the Carter twins. She shares her parents' prejudice and outright hostility toward the local culture. She actively bullies Maia out of jealousy and spends her time demanding new clothes or scheming to acquire more money.

Beatrice is the second Carter twin. She acts as a mirror to her sister, displaying identical cruel behaviors and extreme entitlement. She refuses to learn about her surroundings and relies entirely on the servants to cater to her daily demands.

Professor Glastonberry is the curator of the local museum and a dedicated naturalist. He actively protects Finn's whereabouts from investigators and provides a safe haven for the children when they need to hide from authorities.

Trapwood is a darkly clad private investigator hired to track down the missing Taverner heir. He struggles to move through the unfamiliar rainforest terrain and frequently falls for misleading clues left by uncooperative locals.

Low is the second private investigator tasked with bringing the Taverner boy back to England. Like his partner, he finds the rainforest deeply unpleasant and lacks the cultural tact necessary to gather reliable information.

Colonel De Silva is the Manaus police chief. He uses his position of authority to deliberately mislead the British investigators, prioritizing the safety and freedom of the local people over foreign demands.

Mr. Murray is the lawyer responsible for managing the trust fund left by Maia's deceased parents. He arranges her placement with the Carter family, completely unaware of their true financial motivations.

Sir Aubrey is the aging master of the Westwood estate in England. Following the death of his older son, he becomes determined to locate his estranged grandson in Brazil to secure the family lineage.

Sergei is the son of a Russian count living in Manaus. His family holds significant wealth and social influence, which Mrs. Carter desperately covets. He treats Maia with kindness and defends her against her bullies.

Furo is a stoic Indigenous Brazilian who works as a boatman and servant for the Carters. Despite his employers' harsh treatment, he looks out for Maia and helps facilitate her secret excursions.

Mr. Goodley runs the traveling theater troupe known as The Pilgrim Players. He exploits young actors like Clovis, prioritizing ticket sales over the children's comfort or well-being.

Mrs. Goodley co-manages The Pilgrim Players. She keeps her young actors living in squalid conditions and constantly threatens them with dismissal if their performances falter.