"So you really are the Thief Lord," the stranger said quietly. "Well, keep your mask on if you don't want to show your face. I can see that you are very young." The Thief Lord is the mysterious leader of a gang of children in Venice, whom he supports by selling the loot from his raids. No one knows his name or his origins. Not even Prosper and Bo, two runaways who have found refuge with the gang while fleeing from their aunt and the detective Victor. When Victor actually gets on the children's trail, he puts everyone in danger. But it seems that the gang's community is about to break apart completely when a mysterious assignment from the enigmatic Conte leads the children to a lagoon island. This island, appearing deserted and lonely from the outside, holds a secret that changes everything.