The Ritz-Carlton in Saudi Arabia's capital bills itself as an "elegant oasis" that "completely envelops its discerning guests in majestic surroundings."

But a year ago Sunday, on Nov. 4, 2017, the ultra-luxurious Riyadh hotel — with its marble floors and vast indoor swimming pool — became a gilded prison, when hundreds of Saudi royals, billionaires and senior government officials were detained in an extraordinary power play by the heir to the throne, Crown Prince Mohammed bin Salman.

The involuntary guests were told they had to sign away large chunks of their assets to be released. The detention involved both psychological abuse and — in some cases — torture, current and former U.S. officials say.