The African elephant is the biggest land mammal on Earth and Botswana is home to more than anywhere else in the world. It's the setting for a titanic battle. Every year, thousands of elephants trek over 7,000 miles in search of food and life-giving water. But the desert is a hostile place, especially as the dry season takes hold, so the elephants must use their strength and cunning to survive. Along the way, they are shadowed by some of the most ruthless predators on earth - lions.