Unraveling Raoul Wallenberg's Secrets

"One reason [for keeping this secret] is that there is someone alive who was part of the Soviet government who participated in the decisions about Wallenberg, and would be held accountable if the truth got out," Makinen told TIME. He can think of few other reasons why the Russians are unwilling to cooperate in resolving the issue — particularly if it believes the official Soviet account of Wallenberg's death is the truth.

But researchers also fault Sweden for failing to insist that Moscow release the information that would resolve the issue. "We know for sure that there is plenty of important documentation in Russian archives we have not seen at all," says Berger. "And, for whatever reasons, Sweden is not pushing very hard to get access to it."

So why do the researchers persist, in the face of such stonewalling, more than six decades after Wallenberg disappeared?

"It's a question of principle," says Berger. "Millions of people suffered and died in Soviet captivity. Raoul Wallenberg is symbolic of all these people. It's like Wallenberg's brother once said: 'Yes, millions died, but I want to know about this one.'"