Mr. Huang was rearrested, he told me, with police officers making clear that action was “directly in retaliation” for the column. He spent the next two years in the Luoyang detention center, in a 300-square-foot cell that held as many as 34 other prisoners, according to a lawsuit Mr. Huang filed this month against Silvercorp in Vancouver.

In September, The Globe and Mail of Toronto published a long article on Mr. Huang and Silvercorp, including statements Mr. Huang had made during an interview while he was out on bail. That made the police even angrier, Mr. Huang said in his lawsuit. He was required, according to the suit, “to scrub the sick bay using his bare hands.”

Mr. Huang told me the Luoyang detention center “is the most unbearable imprisonment in China.” He has not seen most Chinese jails, of course, but he said it was much worse than the Beijing detention center, the other one he has seen.

Image Kun Huang, a Canadian citizen born in China, was arrested there after researching a Vancouver silver-mining company. Credit... Kim Stallknecht for The New York Times

Finally, in June 2013, he was charged with criminal behavior and convicted in a one-day private trial in September. He was fined 500,000 renminbi, about $80,000, and sentenced to two years in prison. He was given credit for the time he was jailed after his second arrest and was released and deported in July.

What was his crime? An appeals court decision that rejected his appeal said he committed “the crime of impairing business credibility and product reputation,” according to a translation of the decision provided to me by Silvercorp. He was acquitted of the second charge, that of illegal use of spy equipment — the cameras that filmed the trucks leaving the mine. He had not been the one who bought the cameras or did the filming. Nor had he written the reports, although he did provide information for them.

The appeals court ruling sounds as if simply selling stocks short is a crime under Chinese law. “This court has determined that Huang Kun clearly knew that the purpose of gaining production information and pictures of the said Chinese enterprises, as requested by Carnes, was to short the stocks,” the judges wrote.