The strong brotherly bond between the teenage Prosper and his much younger brother forms the core of this enchanting film, and the story takes pains to examine the meaning of family. As Prosper spends more time with the Thief Lord, he uncovers a huge secret about his new friend's background. Add to the mix the boys' horrid aunt Esther, who has adopted the adorable Bo but finds his brother too much trouble and has consigned him to an orphanage, and it's clear that in this story, families are defined by affection and concern rather than blood.
This is a tough message for children to absorb, but the film pulls it off gracefully by introducing a hint of magic. While the older kids are absorbed in planning the heist, Bo gradually discovers that the object they are seeking may have mystical properties that, initially, only he can discern. Once the rest of the group learns the truth, Prosper and the Thief Lord must make a difficult decision that could change, forever, their relationship to the rest of their improvised family. It's difficult to see these kids forced to make such an adult decision, but it makes for a powerful, and deeply moving, movie that will resonate with both children and adults.