Nicholas C. went to the Soviet Union in 1947 as a tourist, planning to stay three weeks. He ended up staying 34 years - in a Siberian prison camp.
Most incredible of all, Nicholas was fortunate, according to evidence compiled by journalist Patrick Meney in a new book just released here, ''The Broken Hands of Taiga.''
Although desperate pleas on Nicholas's behalf from the French foreign minister forced his release in 1981, Mr. Meney reports that as many as 600 other Frenchmen continue to be held in Soviet prisons. He says many have been imprisoned since World War II, when they were liberated from German prisoner-of-war camps in Eastern Europe by the Soviet Army.
The plight of other foreigners in the gulag, most of them East Europeans and especially Volga Germans, has long been well known. But this is the first time the Soviets have been accused of holding large numbers of Frenchmen.
The French Foreign Ministry confirms Meney's story of Nicholas C., whose identity is not revealed to protect him. It also hints that the harrowing material in the rest of the book could be true.
''In Russia there are a certain number of Frenchmen imprisoned,'' a Foreign Ministry official said. ''These are usually people who are also Russian citizens - and the Soviet Union does not recognize double nationalities. We are constantly making efforts to help them.''
Nicholas's case, as Meney tells it, is unusual because he never was a Soviet citizen. Nor was he a prisoner of war who was liberated, then incarcerated.
Instead, after he traveled through the Caucasus Mountains during the Stalin era, the secret police arrested him on charges of espionage. At his trial, he was acquitted. Nonetheless, the police rearrested and imprisoned him.
For the next 37 years, Nicholas lived either in a prison camp or confined to a remote village near Gorky. Finally, in 1979 he was able to escape KGB surveillance and head to Moscow. A friend brought his case to the attention of French diplomats - and they arranged for Nicholas to be hidden in the embassy.
Only after two years of arduous negotiations with the Soviet authorities was Nicholas allowed to return home to France.
Meney contends that the French Foreign Ministry has papers on about 300 more Frenchmen trapped in the gulag. Although there are no documents offering proof, he adds that diplomats in Moscow told him as many as 300 more French citizens may be imprisoned.
These figures do not take into account the 15,000 Alsatian soldiers who were enlisted in the German Army during World War II and then imprisoned by the Russians.
The Russians evidently considered these men German, not French, citizens.
Even with Meney's book, not much is known about the fate of these French prisoners. Meney says the Foreign Ministry here remains prudent in commenting on the issue, for fear of upsetting delicate negotiations. And Nicholas was warned before he was liberated not to talk about his experiences.
But two years after returning home, he agreed to be Meney's witness.
''He is worried,'' Meney explained in an interview with Paris Match.
''One wonders if keeping these things secret is a good thing. While it seems that Soviet public opinion doesn't count for anything in the country's internal affairs, international opinion can, to a certain extent, improve things.''
In 1981, for example, Soviet physicist and human rights activist Andrei D. Sakharov and his wife, Yelena G. Bonner, staged a hunger strike when the authorities would not allow Bonner's daughter-in-law, Liza Alekseyeva, to emigrate. After 17 days she was allowed to leave the country.