Welcome to the magical underworld of Venice, Italy. Here hidden canals and crumbling rooftops shelter runaways and children with incredible secrets....After escaping from their cruel aunt and uncle, orphans Prosper and Bo meet a mysterious boy who calls himself the "Thief Lord." Clever and charming, the Thief Lord leads a band of street children who enjoy making mischief. But the Thief Lord also has a dark secret. And suddenly Prosper and Bo find themselves on a fantastical journey to a forgotten place. What they discover there will change the course of their destiny ... forever.