A foul cell in a Moscow detention center was about the last place an American businessperson named Michael Calvey expected to find himself after spending 25 years building a flourishing venture capital firm in Russia that transformed some tech startups into global brands.

First, beefy agents from the FSB, the federal security service, ransacked his apartment before dawn. Hours later he was confined to a holding cell with two other inmates and a filthy hole in the floor for a toilet.

“The cell is stuffy and hot, an oppressive stench hanging in the air as if from accumulated decades of human sweat mixed with the indescribable horrors emanating from the toilet hole area,” Calvey wrote in a new book out this week called “Odyssey Moscow.” It details his extended ordeal through the Russian court system in a fabricated fraud case initiated in 2019: “In the course of a few surreal, terrifying hours I have morphed from one of the most successful Western businessmen in Russia into a prisoner of the state.”

Perhaps no Western businessperson promoted foreign investment in Russia more than Calvey, 57, who helped to forge internet titans from tech startups like Yandex — a version of Google, Amazon and Uber rolled into one — or Tinkoff Credit Systems, one of the world’s biggest digital banks. The firm he founded, Baring Vostok Capital Partners, earned colossal returns.

Then Baring Vostok got mired in a nasty commercial dispute with two dubious Russian partners who were stripping assets out of a bank in a troubled merger. Once, Calvey’s empty Moscow apartment mysteriously caught fire hours before a dinner involving tense negotiations.

After his firm filed a case with a London arbitration court, the partners convinced Department K of the FSB, responsible for internal financial crimes, that the American and several partners had perpetuated a massive fraud as part of a dastardly foreign plot to undermine Russia’s financial sector.

The agents pounced in February 2019, and although no evidence of wrongdoing ever emerged in court, Calvey and several partners spent years in jail or under house arrest.

“Once the FSB gets involved in a case, they’re like a car with six gears going forward and none in reverse,” Calvey said in an interview in Switzerland, his home since finally being allowed to leave Russia in 2022. Lanky and trim, he retains a boyish air despite his gray hair. “They will never back up or lose face.”

His arrest stunned Western investors. “Everyone I knew was incredulous, angry and shocked,” said Bernie Sucher, an American banker with extended experience in Russia. “It was viewed as a direct assault on the very idea of long-term investment in the Russian economy.”

Unusually, dozens of influential Russians defended Calvey. They included Kirill Dmitriev, the head of Russia’s sovereign wealth fund and now a key negotiator for ending the Ukraine war; German Gref, the CEO of Russia’s largest bank; and Alexei Kudrin, a previous finance minister. The U.S. Embassy in Moscow also objected strenuously to his arrest.

Calvey thought such interventions, combined with the blow to investor confidence, would get the case dropped. But nothing outweighed the FSB.

Russian President Vladimir Putin did summon top Kremlin officials, ordering them to get the American businessperson out of prison, but also to find something illegal that Calvey had done, he said he later learned. At a tense time in U.S.-Russia relations, the Kremlin could not admit to arresting a prominent American businessperson on false pretenses, he said.

Released from prison after two months, Calvey was confined to his apartment with an electronic monitoring device strapped around his ankle for two years, and spent a third under court-ordered supervision with an 8 p.m. curfew.

When he developed a cancerous tumor in one leg, the court refused to allow him to remove the device, so doctors operated without benefit of an MRI.

The Russian Foreign Ministry and the Russian Embassy in Washington did not respond to requests for comment about Calvey’s account.

When first arrested, Calvey was jailed in Matrosskaya Tishina prison, near downtown Moscow. It is sometimes called “Kremlin Central” because so many inmates face charges in high-profile corruption cases pushed by the Kremlin. There were no violent criminals, but nobody is ever acquitted, either, Calvey wrote.

His cellmates greeted him with a nonalcoholic toast: “Novoselye,” or welcome. One was a former deputy minister of culture. Another was an army general. A younger one was a computer hacker, and three were construction moguls. Trust nobody, one of them confided.

Their cell, 13 feet by 16 feet, was tidy and somewhat comfortable, with a television and a separate toilet. The men shared everything equally from cleaning chores to food supplies from outside. He dedicated his book to the men of Cell 604, and tears up when he talks about them. The book will be released Thursday in Britain and in early April in the United States.

In August 2021, Calvey was convicted of the misappropriation of funds and given a five-year suspended sentence. The conviction on false charges grated, he said, a stain on all his work for Russia.

Calvey’s businesses thrived even while he was imprisoned, and he pulled the plug only after Russia invaded Ukraine in 2022. The hasty disinvestment cost his company billions of dollars, he said.

He is done with Russia. Although under Russian law his conviction was nullified after his five-year probation period ended a year ago, last week a Moscow court changed the probationary sentence given to a French defendant in the case to a prison term in absentia.

The simmering geopolitical differences between Moscow and Washington mean that any businessperson can become a chessboard pawn, he said, adding: “You may hope that you’re not going to get stepped on the head, but ultimately it could happen at any time.”