If you've ever been to China, you've probably seen that people enjoy practicing different forms of qigong (energy) exercises outside, mostly in parks. However, back in the early 1990s, there was one slow-moving meditative exercise system that was becoming increasingly popular before almost all of its practitioners disappeared overnight.

Tens of thousands of people, from all strata of society and of all ages, who came together each morning in different public parks throughout communist China to perform this qigong's gentle exercises for an hour or two before heading off to work or school, were suddenly nowhere to be seen after the fateful day of July 20, 1999.

What was this practice? Why were people so drawn to this particular meditation system? And why had all these common, law-abiding citizens disappeared?