The Chinese Communist Party is notorious for the ruthlessness with which it pursues its opponents, but what is less well known is how viciously it sometimes treats its own members.
Since a major anti-corruption campaign was started by the President, Xi Jinping, at the end of last year, glimpses have emerged of the torture that wayward party members are subjected to, sometimes fatally.
The system is run by the Central Commission for Discipline Inspection, an arm of the party that operates above the law.
Since January, about 2300 officials have been "disciplined" by the system known as "shuanggui".
At the beginning of March, an important Communist Party official in the northern city of Dandong vanished. For 24 hours, no one knew what had happened to Guan Shaofeng, 50, a biologist who ran the inspection department at the city's custom house.