Early last year, at a royal encampment in the oasis of Rawdat Khuraim, Prince Mohammed bin Salman of Saudi Arabia visited his uncle, King Abdullah, in the monarch's final days before entering a hospital. Unbeknown to anyone outside the House of Saud, the two men, separated in age by 59 years, had a rocky history together. King Abdullah once banned his brash nephew, all of 26 at the time, from setting foot in the Ministry of Defense after rumors reached the royal court that the prince was disruptive and power-hungry. Later, the pair grew close, bound by a shared belief that Saudi Arabia must fundamentally change, or else face ruin in a world that is trying to leave oil behind.