In 2015, the North Korean diplomat Thae Yong Ho received an unusual assignment. Kim Jong Chol, the older brother of North Korean leader Kim Jong Un, was coming to London to attend an Eric Clapton concert, and Thae, who was then stationed in London, was assigned to look after him. Providing direct service to the ruling family confers honor on North Korean officials and their households, so Thae expected his two sons to be impressed.

To Thae’s surprise, his sons were outraged. Ordinary North Koreans could be expelled from university (or worse) for listening to Western music, they told him. And now the Kim family was spending thousands of dollars in a single evening to enjoy entertainment forbidden to all other North Koreans. In the eyes of his children, Thae later wrote in his memoir, Password to the Third Floor , he was a prisoner forced to take care of a prison warden. Their reaction left him ashamed.

The next year, Thae, his wife, and their sons escaped to South Korea .…