Ben Fogle leads a team of deserving heroes on the final leg of his epic South American adventure from the Equator to the Tropic of Capricorn. In this episode, they cross the legendary Atacama Desert in Chile, the driest place on earth, in a bid to summit Volcano Corona. Ben leads his team across the Atacama salt plains with their razor-sharp salt crystals. But exposed in this vast desert with no shade from the scorching sun, district nurse Katie suffers intense pain from her blistered and swollen feet. As they climb ever higher into thinner air, the crippling effects of altitude start to kick in and they struggle to catch their breath. Air ambulance paramedic Haydn collapses in camp and Ben suddenly faces a medical emergency.