The first sign something was amiss came when an 18-wheeler lumbered into the dilapidated neighbourhood of Paseos del Valle on the outskirts of Guadalajara.The truck itself was unremarkable – a white tractor unit pulling a refrigerated tailer emblazoned with a polar bear logo – but it came with a police escort.And as the massive vehicle pulled onto a muddy track between the last row of houses and a cornfield, dogs across the neighbourhood began to bark wildly at the overpowering stench it released.“It was a smell of death,” recalled Alejandro Espinosa . . .