Investigation. a police officer arrives and we're told we need to leave for our own safety. we do. but not before we spot a red truck loaded up and leaving the very same market. it matches the distinctive red of the trucks used by one of the main international cobalt supply firms. china's congo mining. we decide to follow it. we can't afford to lose him. because where he delivers that cobalt load, that is the link between the children that you saw down there on the river front and the global markets. as the truck pulls into its final destination, guards rush out to block our cameras. >> stop. ...