Simon visits Brazil, the biggest country on the continent. He starts in one of the remotest regions of the Amazon, with the Waiapi people, who cling on to their traditional way of life, which is under threat from logging and mining interests. The tribal leaders argue that preserving the forest is not only crucial to moderating the Earth's climate; they are working with Brazilian scientists to show how the Amazon can be managed to produce valuable crops and lifesaving medicines, without destroying the environment. At this point, in early 2020, Simon's journey was interrupted by the Covid pandemic, and he returns two years later to see how Brazil became one of the countries worst hit by the virus. In Manaus, the city at the heart of the Amazon, he visits a neglected indigenous neighbourhood and meets the nurse who was the only source of healthcare during the pandemic. On the outskirts of Manaus, where the Amazon jungle meets the city, he catches bats with a veterinary scientist who is hoping to identify potential future pandemics, before they enter the human population. Simon ends this leg of his journey on the west coast of Brazil, in the iconic city of Rio de Janeiro, a city under threat from climate change, vulnerable to flash floods and baking heat. The government has built a high-tech NASA-style control room to monitor all parts of the city for potential disasters. And in one favela, Simon meets the woman who has planted an urban forest to cool her neighbourhood, as well as to grow fresh food for many of the neglected children.

Simon travels through three of the world's most extreme environments: the salt flats of Bolivia, the Brazilian Pantanal and Paraguay's Chaco Forest. In Bolivia, Simon meets a family who makes a living carving salt from the vast white expanse of the Uyuni salt flats, so huge it is said to be visible from the moon. He learns that beneath the salt could lie huge reserves of lithium, the metal so crucial for the batteries that will fuel the next generation of electric cars. Crossing into Brazil, Simon visits the world's largest wetlands, the Pantanal, and has a close encounter with South America's apex predator, the jaguar. Drought and fire threaten the Pantanal, but so too does excessive flooding, and Simon meets a farmer who has spent years building dams to hold back the rising waters and save his family farm. The last leg of this journey takes Simon into the little-visited Paraguay, where he meets a unique community which, despite their small numbers, has had a huge impact on the economy and environment of the country. Mennonites originally hail from Europe but they have spread throughout the world. In Paraguay, many live in ultra-conservative communities and eschew many of the trappings of the modern world. They drive around in horses and carts and speak their own language, known as low German. Simon visits a school where traditionally clothed children are drilled in bible texts and there are no smartphones to be seen. But the Mennonites have been hugely successful farmers, embracing modern methods where necessary to found vast cattle ranches and soy farms. They have chopped and burned huge areas of the Chaco, the unique dry spiny forest, which is twice the size of Spain and dominates the centre of the South American continent. Perhaps inevitably, this economic miracle, which has turned Paraguay into a major player in the global food market, has had its victims and Simon ends this leg of his journey with the Ayoreo people. Following a history of persecution and having lost much of their land, the Ayoreo now mount armed patrols to defend what remains. Others have given up the modern world altogether and returned to the hunter-gatherer lifestyle of their parents and grandparents, living in the harsh dry forests of the Chaco.