visible forms of slavery. china, a fast-developing, fast-growing economy, how big of an issue is slavery in china? >> reporter: well, andrew, there are no official numbers, but there is, of course, a dark side to this economic growth. and that is the abuse and enslavement of workers. there have been several cases where people have been sucked into factories to try to meet all of the production demands. and some of the most vulnerable here in china are the mentally ill and the mentally challenged. there have been cases recently of mentally challenged people who have been sold into factories, forced to work without pay, sometimes beaten, sometimes fed dog food. and a lot of times these people are the most vulnerable because of the fact that they can work and at the same time they are easily manipulated, andrew. >> are there laws in place to protect these sort of people? these victims in china?