Overview: Janina Ramirez travels to Mexico, where, just before the outbreak of WWII, American husband-and-wife explorer team Matthew and Marion Stirling were lured into the jungle by the legend of a colossal stone head. They found the head – and a lot more than they bargained for – because it turned out to be the first clue in a trail that led to the discovery of a lost civilisation, now known as the Olmecs.