Zhang Dongdong has been fielding ever more requests for legal advice from jittery entrepreneurs, nervous government officials or their desperate relatives. They usually do not tell him the whole story, and sometimes say it happened “to a friend”, but most want to know the same thing: what to do when they are targeted by China’s corruption busters. “Some had received a tip-off that they were being investigated, some got a call from disciplinary inspectors asking them to cooperate, but in most of...