(Foreign Policy) It was a story for our febrile super-connected times. But it was also a story from the past one that recalled those far-off days when mole hunting was the sport of every revolutionary cadre. When protesters occupying the Hong Kong airport thought they had detected an infiltrator in their ranks they frisked him and found that the name on his passport matched that of an auxiliary policeman from the nearby city of Shenzhen. The demonstrators denounced Xu Jinyang tied him up roughed him up and spent three hours wondering what to do next. The consensus was to keep kicking hima decision that might have led to his death had it not been for the intervention of a local reporter Richard Scotford who shielded the accused man and warned the crowd that his ill treatment would be a propaganda coup for the mainland. He was right. Footage of these events became Exhibit A for commentators arguing that the Hong Kong pro-democracy movement was violent and reprehensible. Whoever Xu Jinyang wassecurity agent undercover police officer freelance troublemaker or innocent bystanderhe had done his bit for the Chinese Communist Party. The impulses thrumming in this story are familiar to many with experience of the hot zone of radical politics. The circuit of infiltration suspicion accusation violence and confusion is a durable part of the relationship between the state and its most radical discontents. During phone interviews with survivors of the revolutionary movements of the 1960s and 1970s Im used to hearing them remark on unusual clicks or echoes on the linean experience familiar to Chinese dissidents and Hong Kong protesters today.