The Thief Lord recap

Orphaned brothers Prosper and Bo flee to Venice when their aunt plans to adopt Bo alone. They join homeless children living in an abandoned cinema under Scipio, the celebrated Thief Lord. Detective Victor Getz tracks them but becomes their ally. A mysterious client commissions Scipio to steal a wooden wing belonging to Ida Spavento; the children learn it completes a hidden merry-go-round able to change a rider's age. They also discover that Scipio is really the sheltered son of a wealthy doctor and has been stealing from his own home. After the wing is recovered, the group follows it to a secret island. Scipio uses the restored carousel to become an adult, while crooked dealer Ernesto Barbarossa is turned into a young child and the machine is destroyed. Ida provides a home for Prosper, Bo, and the other children. Adult Scipio joins Victor's detective agency, and Prosper and Bo remain safely together in Venice while their aunt unwittingly adopts the child-sized Barbarossa.

After their mother's death, twelve-year-old Prosper and five-year-old Bo run away to Venice because their aunt Esther Hartlieb wants to adopt Bo but send Prosper away. Esther hires private detective Victor Getz to find them. The brothers are already living with a group of homeless children in the abandoned Star-Palace cinema: Hornet, Riccio, Mosca, and their admired leader Scipio, who calls himself the Thief Lord. Scipio brings valuables he claims to steal from rich Venetian houses, and crooked antiques dealer Ernesto Barbarossa buys them for much less than they are worth. Prosper dislikes depending on theft but accepts the shelter to keep Bo safe. Victor searches hotels and streets, gradually following reports of two foreign boys and the traces left by the group, while Bo's friendliness makes secrecy increasingly difficult.

Victor's investigation brings him closer to the Star-Palace, and the children realize an adult is asking questions about Prosper and Bo. At the same time, Scipio receives an unusually large commission from an elderly man calling himself the Conte. The requested object is a wooden lion's wing kept in the home of photographer Ida Spavento. The payment could secure the group's future, so Scipio accepts despite Prosper and Hornet's doubts. The children begin watching Ida's house and planning an entry. Victor uses disguises and patient surveillance to follow them, but his encounters with Bo and what he learns about Esther's plan make him less willing to treat the case as a simple recovery of missing children. The chase now threatens both the gang's hiding place and Scipio's promised theft.

The children catch Victor near their hideout and hold him in the cinema, only to discover that the detective is more sympathetic than their fear suggested. He promises not to deliver Prosper to an institution or help Esther separate the brothers. Their investigation of the wing leads them to Ida Spavento, who surprises them by listening and explaining its history. It once belonged to a magical merry-go-round whose figures could alter the age of anyone who rode them; the carousel was hidden on the Isola Segreta, and the missing wing may allow it to work again. Victor also follows Scipio and exposes another secret: the supposed master thief is the school-age son of wealthy Dottor Massimo. His loot has come largely from his own family home. Hurt by the deception, the gang must decide whether to finish the Conte's commission without trusting its leader.

Scipio admits that his Thief Lord identity gave him freedom from a humiliating and tightly controlled life at home. Although the others resent his lies, the group continues the plan with Ida and Victor involved. They secure the wooden wing and arrange its delivery, then learn that the Conte is Renzo, who wants the restored carousel for himself and his sister Morosina. The promise of a machine that can make children older or adults younger changes the meaning of the theft for everyone, especially Scipio, who longs to escape his father's power. Barbarossa learns enough to pursue the valuable secret as well. The children and Victor prepare to follow the wing toward the lagoon's forbidden island rather than let the mysterious clients disappear with it unobserved.

On the Isola Segreta, the wooden wing is returned to the lion figure and the merry-go-round's power proves real. Renzo and Morosina use it to shed their old age. Scipio chooses to ride in the direction that makes him older, transforming his child's body into that of an adult so that his father can no longer command him. Barbarossa, driven by greed, interferes with the machine and is carried in the opposite direction, becoming a small boy. The struggle leaves the carousel damaged, preventing the others from using its magic at will. The transformations solve none of the group's practical problems by themselves: Prosper still wants only to remain with Bo, the cinema is no longer a secure secret, and the children need an enduring home. Victor and Ida turn their attention from pursuit and adventure to protecting them.

With the merry-go-round broken, Renzo and Morosina depart in their restored youth. Scipio remains physically adult and refuses to return to Dottor Massimo's household. Victor takes him on as an assistant in the detective business, where his costumes, confidence, and knowledge of Venice become useful without requiring him to pretend to be a criminal leader. Ida opens her home to Prosper, Bo, Hornet, Riccio, and Mosca, allowing the children to stay together and return to school. Prosper no longer has to choose between surrendering Bo and living as a fugitive. Esther Hartlieb fails to gain custody of Bo, but the transformed Barbarossa looks like the charming young child she wanted. She takes him into her household without understanding that he retains his adult greed and bad temper. The brothers remain in Venice among friends who have become their family, and the old gang begins a safer life after the end of the Thief Lord's rule.

The restored merry-go-round on the Isola Segreta can change a rider's age. Renzo and his sister Morosina use it to regain their youth. Scipio, tired of being powerless under his father's authority, rides until he has an adult body. Barbarossa tries to seize the magic for himself and is transformed into a small boy; the carousel is then damaged beyond further use. The newly adult Scipio does not return to his old home. He becomes Victor's assistant, putting his talent for disguises and investigation to legitimate work. Ida Spavento gives Prosper, Bo, Hornet, Riccio, and Mosca a safe home and the chance to attend school while remaining together. Esther Hartlieb no longer gets to separate the brothers. Instead, she takes in the child-sized Barbarossa, whose angelic appearance conceals the same greed and bullying temperament. Prosper and Bo remain in Venice with their chosen family, while Scipio gains independence without retaining the enchanted power that changed him.