Or so a Russian informant–call him Ivan, a pseudonym-alleges in a confidential Pentagon report obtained by NEWSWEEK. Amid the excitement and doubt raised by President Boris Yeltsin’s talk of POWs in Russia, Ivan’s account tantalizingly suggests that at least one American serviceman could still be among the living. His story may not hold up under scrutiny. But since June 10, Ivan has provided U.S. investigators in Moscow with highly detailed accounts of Marken, whom he claims he befriended between 1982 and 1986 while serving as a fellow inmate of PL-350/5. U.S. sources say that Ivan, who is being held in a Moscow safe house, has been threatened by former KGB officials, warning that he will be jailed again if he talks.

Ivan’s story begins in 1982, when he says he met Marken on a prison barge en route from a camp in Arkhangelsk Province to PL-350/5, where the two spent four-and-a-half years together. He describes the American as a tall, frail and stooped 60-year-old, who had a shaven head, scars on his left shoulder and left forearm and a name tag on his prison uniform identifying him as “Marken,D.” “Apparently psychologically broken,” but also “polite and soft-spoken,” the report says, Marken was an easy target for other inmates; Ivan came to his defense and was rewarded with a grim account of his life in the gulag. Shipped off to Korea in 1952, Marken ejected from his plane in 1953 or 1954, and later spent eight or nine years in Soviet psychiatric hospitals. Fitted with a straitjacket, he was “given injections of aminazin and other unknown drugs to make him sleep.” A different drug made his hands “twist inward.” Over the next two decades, says Ivan, Marken moved from camp to camp every 12 to 18 months.

His life in PL-350/5 was hardly a step up. Like the other 600 or so inmates, Marken milled logs cut from the surrounding dense taiga, ate meals in the mess hall, used the latrine and bathed once a week. But, according to the investigative report, he “was treated worse than other prisoners” and was harassed by guards for minor infractions like wearing his cap askew. Three reprimands earned him a trip to the “karster,” the solitary-confinement box ringed by barbed wire, where he spent a good deal of time. But Marken, who by this time had taught himself Russian, kept a low profile, hoping to conceal the fact that he was the only American in the camp. Ivan, released from PL-350/5 in 1986, says he returned three years later to bring his friend a package of cigarettes, tea, onions and sausage. Climbing to the top of a lumber pile, he hailed one of the inmates. Is the old man still alive? he asked, meaning Marken. " Yes," came the answer. “This is for [him],” he said, tossing the packet over the stone fence. That was the last Ivan heard of Marken.

A gripping tale-but is it true? Late last week, U.S. and Russian investigators flew to Pechora to check out Ivan’s story. An examination of documents at PL-350/5, as well as archives pertinent to other camps in the penal colony, turned up 23 people named Marken (or Merken) who had been inmates. But none fit Ivan’s description of David. “We don’t have any Americans here,” Maj. Gen. Leonid Khamluk, chief of some 10 prison camps in the Pechora region, told an AP reporter. Prison staffers and inmates who had been at PL-350/5 in the 19821986 period couldn’t recall ever seeing an American or a foreigner in the camp, which houses mainly common criminals.

While Russian team members want to close the book on David Marken, U.S. investigators aren’t yet willing to give up. Spurred by the chance that Marken isn’t a fiction-and that he’s still alive in some other camp-they flew back to Moscow to question Ivan further. The trail of clues is narrow, at best. David Marken isn’t on the Pentagon’s official list of casualties and MIAs in the Korean War. But experts say that list excludes 11,000 U.S. casualties. Both Russian TV and the Ark Project, a private U.S. group, suggest that the missing American has a different name, Robert Martin. Could he be David Marken? By rekindling the hope that U.S. POWs may still be alive in Russia, Yeltsin sought to bury decades of suspicion between the two countries. Instead, he has raised an awful specter that has haunted America for 40 years.