One morning last November, at around 4 in the morning, guards at Dongguan Prison, in southern China, entered the cell where Mark Swidan was sleeping and started shaking him and telling him to get up.

He was 49, and he had spent the past 12 years and 14 days behind bars for committing a crime—conspiring to manufacture drugs—that nobody in Washington, D.C., believed he had committed.

For more than a decade, he had been in a windowless box with 31 other men—it was roughly 30 feet by 10 feet, or a little less than 10 square feet per human being—and he had spent at least two additional years in solitary confinement. He was no longer sure exactly how long it had been.

“I’m not good with time anymore,” he told me.

That morning, time moved very fast.

“It was very hurried,” Swidan said. “They didn’t want anybody else in the block to know. I didn’t have time to brush my teeth. They just led me into this van.”

The windows of the van were blacked out, and they started to move through the early morning dark. “There was a long line of police cars, all white, in front of us, behind us,” he said. “It was surreal.”

It was the first time Swidan had spoken to a reporter since coming home from China seven months ago, and when he talked about these things, he had an almost dreamlike, drifting quality, as though he were trying to figure out what had happened to him.

Now we were in a steakhouse in Houston, his hometown, and it was hazy and swampy and overcast outside. He wore a black tuxedo jacket and creased loafers that he hadn’t worn in many years, and he sat next to his girlfriend, Syndi Vo, who, Swidan said, was “an influencer.” His sunglasses were pushed above his forehead. He was focused, he said, on “putting my life back together,” which he had dreamed of doing when he was behind bars but now, in America, seemed nearly impossible...