Setting off in Tanzania, they travel over the Ngorongoro Crater, where one of the world's densest concentrations of game inhabits an enormous extinct volcanic crater. Landing in the Serengeti, Stephen shadows a local vet on his rounds treating the wildlife of the famous national park. Then he takes to the air again, this time heading westward into the dense forests of Rwanda's Volcanoes National Park in search of one of the planet's most awe-inspiring animals - the mountain gorilla.