In the end, it was only an inconvenience. But what if he'd been in, say, Finland when that notice popped up? The Finns are fine people, but they also have a 500-mile border with Russia. Would letting Browder go be worth risking an international incident with a bigger, more aggressive neighbor? He can make a reasonable case that, no, he would not be worth it. "I'm very realistic about who's coming to my defense," he said. "I am my defense."

So he's careful. He avoids countries that might be friendly to Putin. Much of the Third World is out. So is Hong Kong. He'd be fine in Japan, but only if he didn't fly over Russian airspace. What if the plane has trouble and makes an emergency landing in Novosibirsk? That's where Khodorkovsky was seized and hauled off to a cage.

Even in London, he's cautious. He won't talk about his family or where he lives. He varies his schedule and his route to work every day. He doesn't eat in the same restaurant twice in succession, or in any restaurant with predictable frequency; Russian agents have reputedly twice poisoned dissidents in London. He told me the British government has rebuffed at least a dozen requests to extradite him, and American intelligence has warned him that Russian agents planned to grab him off the street.

Years ago, a Russian living in London came to Browder's staff with information about certain wealthy, corrupt people in Moscow. He was cagey and shifty and, at first, it seemed like he might be a Russian agent trying to plant false clues. But his information checked out and Browder learned who he really was. His name was Alexander Perepilichnyy, and he was nervous because he believed he was on a Russian hit list.

On November 10, 2012, Perepilichnyy dropped dead in front of his house in Surrey. There was no obvious cause of death—no heart attack or stroke or aneurysm—and an inquest wasn't opened until last June. Perepilichnyy wasn't a well-known dissident, so no one thought to take a hard look when he died. "They got away with it," Browder said, meaning the Russians. "That's a perfect example of why you don't want to be an anonymous guy who drops dead."

“Their main objective is to get me back to Russia. And they only have to get lucky once. I have to be lucky every time.”

So Browder is deliberately not anonymous. He does not live in cloistered fear. When a car service got confused trying to pick him up for a photo shoot—definitely a way to not be anonymous—we took the Tube a few stops, then walked through Kentish Town to the studio. There was no security, just two men wandering around London. He has hobbies that he asked I not name, but none of them are solitary or sedentary. "One thing I can tell you," he said, "with the threat of death hanging over you, you live life to the fullest." He laughed a little.

In this new version of his life, Browder is still most often referred to as a financier, but that's only marginally true. He gave all his investors their money back, and manages only his own now. Justice for Sergei—and aggravating Putin—is his full-time job. His staff of 11 tracks money launderers, deciphering which flunky is fronting for which oligarch, sniffing out the rest of that $230 million. He lobbies other governments to pass their own versions of the Magnitsky Act. The United Kingdom has one, as does Estonia. Lithuania is close, and Canada passed one in October. "Unconstructive political games," Putin told a Canadian interviewer immediately after, orchestrated by "the criminal activities of an entire gang led by one particular man, I believe Browder is his name."

And Putin wasn't finished. A week later, Russia slipped another red notice into Interpol's system. For the second time in three months, Browder was temporarily barred from entering the U.S. It's relentless, Putin clawing at him, thrashing. "Their main objective is to get me back to Russia," he said. "And they only have to get lucky once. I have to be lucky every time."

"Everything Bill's done has cost him tremendously," Parker said. "It's cost him money, restricted his personal freedom. And he didn't have to. He was out of Russia. He could have done what many did and walked away. Bad things happen, right? But here's a guy who's proven whatever he needed to prove to himself. He made his money. Now here's a way to find meaning. It's also a debt of honor."

No, it's more than that. "It's penance," Browder said. Sergei Magnitsky was an ordinary Muscovite who happened to work for an American who annoyed Vladimir Putin. "Sergei was killed because of me. He was killed instead of me." He let that hang there a moment. "So, yeah, it's all penance."

Sean Flynn is a GQ correspondent.

This story originally appeared in the December 2017 issue with the title "Putin Enemy No.1."

*Small portions of this paragraph have been rephrased to be more accurate.

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