North Korea is a notoriously difficult country to escape from, not only because of the physical barriers the country erects along its northern border, but because of a sickening form of hostage-taking: High-ranking officials are not allowed to bring their whole families on overseas postings. That ensures that, should the official defect, he knows that his family will face severe punishment back home. That—understandably—ensures that very few take the risk.

One who did last year is Thae Yong-ho, the former No. 2 official at North Korea’s London embassy. Thae, the highest-ranking North Korean to defect in some two decades, was able to escape with his children (indeed, he has said that he did so in part to “cut off this slavery chain” for his sons) but had to leave his brother and sister behind.