Welcome to the magical underworld of Venice, Italy, where hidden canals and crumbling rooftops shelter runaways and children with incredible secrets… Prosper and Bo are on the run from their cruel aunt and uncle. The brothers decide to hide out in Venice, where they meet a mysterious thirteen-year-old boy who calls himself the Thief Lord. Charming and clever, the Thief Lord leads a band of street children who enjoy making mischief. Prosper and Bo are delighted to be part of this new family. But the Thief Lord also has a dark secret of his own. And suddenly Prosper and Bo find themselves on a fantastical journey to a forgotten place. What they discover ther will change the course of their destiny.