It was an easy story to miss. On Feb. 22, the Beijing newspaper China Business Herald, citing an anonymous source, reported that PetroChina International Vice President Shen Dingcheng had been missing for weeks. As a single point of data, the story means little. But the disappearance of Shen (which dozens of other Chinese news outlets covered) is likely another piece of the still unfolding and maddeningly opaque saga of Zhou Yongkang. Shen, it turns out, served as Zhou's secretary for part of the 1990s. Formerly one of the most powerful men in China, Zhou ran China's state security apparatus as...