Officers in Progreso are on the lookout for day-trippers trying to smuggle prescription pills back into America, bought cheaply from one of the 200 pharmacies just on the other side of the border. At the Juarez Lincoln bridge a new recruit is waiting for her first drugs seizure – and strikes gold when she stops an SUV heading for Atlanta. And as night falls on Brownsville, a suspected courier for one of the Mexican cartels is questioned about why she has tried to smuggle $50,000 in cash out of the country.