How can one of the world's most free-wheeling cities transition from a vibrant global center of culture and finance into a subject of authoritarian control? As Beijing's anxious interference has grown, the "one country, two systems" model China promised Hong Kong has slowly drained away in the years since the 1997 handover. As "one country" seemed set to gobble up "two systems," the people of Hong Kong riveted the world's attention in 2019 by defiantly...