From the 2018 report:
It was a life-or-death call. The Chinese government had been systematically picking off American spies in China, dismantling a network that had taken the CIA years to build. A mole hunt was underway, and the former officer, Jerry Chun Shing Lee, was the prime suspect.
The FBI could have arrested him on the spot for possessing classified information. But inside a secretive government task force, investigators argued against it, former U.S. officials recalled. If Lee were a turncoat, arresting him on an unrelated charge would tip off the Chinese and allow them to cover their tracks. If he was not the mole, and some argued strenuously that he was not, an arrest might allow the real traitor to escape.
So the FBI allowed Lee to return to Hong Kong, court papers show, where he hastily resettled with his family. The agents gambled that by watching patiently, they might piece together how China had decimated the United States’ spy network, and determine whether Lee had helped.
Nearly five years later, when Lee made a surprise return to the United States this week, the FBI made its move. He stepped off a Cathay Pacific flight at Kennedy International Airport on Monday. A waiting FBI agent, Kellie O’Brien, called out his name, according to court records. Lee answered, and was arrested.
His apprehension, on the same single charge that could have been brought years ago, is the latest development in one of the most damaging affairs in modern CIA history.
The kicker: “When the CIA noticed in late 2010 that its spies were disappearing, suspicion did not immediately turn to Lee, according to current and former officials. But as fears of a mole grew, the government set up a secret task force of CIA officers and FBI agents. A veteran FBI counterintelligence agent, Charles McGonigal, was assigned to run it, former U.S. law enforcement officials said.”
Now that McGonigal is alleged to have been in bed with the Russians, that sheds quite a light on his drawn-out investigation into Chinese spy Jerry Chun Shing Lee.