The electric vehicle revolution is hotting up, and Tesla is leading the charge. The trillion-dollar car company is now worth more than all the other major car makers put together. But where does Tesla get the rare metal for its car batteries, and how ethical is its supply chain? Reporter Darragh MacIntyre meets the African nuns who say Elon Musk’s company must do better. They’re demanding the world’s richest man does more to protect some of the poorest people on the planet.